View source for List of unusual units of measurement

{{Short description|Units of measurement that are not part of a coherent system}}

An '''unusual unit of measurement''' is a [[Unit of measurement|unit of measurement]] that does not form part of a coherent system of measurement, especially because its exact quantity may not be well known or because it may be an inconvenient multiple or fraction of a base unit.

Many of the unusual units of measurements listed here are colloquial measurements, units devised to compare a measurement to common and familiar objects.

==Length==

<!-- Please keep entries sorted in ascending order of magnitude, smallest first -->

===Horizontal pitch===
Horizontal pitch (HP) is a unit of length defined by the Eurocard printed circuit board standard used to measure the horizontal width of rack mounted electronic equipment, similar to the rack unit (U) used to measure vertical heights of rack mounted equipment. One HP is 0.2 inches (1/5") or {{convert|1/5|in|mm|2|abbr=off|disp=out}} wide.

=== Hammer unit ===
[[Company:Valve Corporation|Valve's]] [[Software:Source (game engine)|Source]] game engine uses the ''Hammer unit'' as its base unit of length. This unit refers to Source's official map creation software, Hammer.<ref>{{cite web |url=https://developer.valvesoftware.com/wiki/Dimensions |title=Distance - Valve Developer Community |access-date=2020-11-29 |quote=Maps, architecture and prop models use a scale of 1 foot = 16 units.}}</ref> The exact definition varies from game to game, but a Hammer unit is usually defined as a sixteenth of a foot (16&nbsp;Hammer units = 1&nbsp;foot). This means that 1 Hammer unit is equal to exactly {{convert|1/16|ft|mm|2|abbr=off|disp=out}} or {{convert|1/16|ft|in|2|abbr=off|disp=out}} (3/4").

===Rack unit===
[[File:Server rack rail dimensions.svg|thumb|upright|A typical section of rack rail, showing rack unit distribution]]
{{Main|Rack unit}}
One ''rack unit'' (U) is {{convert|1.75|in|2}} and is used to measure rack-mountable audiovisual, computing and industrial equipment. Rack units are typically denoted without a space between the number of units and the 'U'. Thus, a 4U&nbsp;[[Server (computing)|server]] enclosure (case) is {{convert|7|in|1|spell=in}} high, or more practically, built to occupy a vertical space seven inches high, with sufficient clearance to allow movement of adjacent hardware.

===Hand===
{{main|Hand (unit)}}
The ''hand'' is a non-SI unit of length equal to exactly {{convert|4|in|mm|1}}. It is normally used to measure the height of horses in some English-speaking countries, including Australia,<ref>{{cite web |url=http://www.equestrian.org.au/site/equestrian/national/downloads/content/attachments/rules/02%20Mch-Nat%20Measuring%20Rules.pdf |archive-url=https://web.archive.org/web/20060826125716/http://www.equestrian.org.au/site/equestrian/national/downloads/content/attachments/rules/02%20Mch-Nat%20Measuring%20Rules.pdf |archive-date=26 August 2006 |title=Equestrian Federation of Australia National Measuring Scheme Effective from 1 January 2002 and amended in March 2002 |author=<!--Staff writer(s); no by-line.--> |date=March 2002 |website=www.equestrian.org.au/ |publisher=Equestrian Federation of Australia |access-date=27 February 2014}}</ref> Canada, Ireland, the United Kingdom, and the United States. It is customary when measuring in hands to use a point to indicate ''inches'' (quarter-hands) and not ''tenths of a hand''. For example, 15.1 hands normally means 15 hands, 1 inch (5&nbsp;ft 1 in), rather than 15{{frac|1|10}} hands.<ref name=omafra>{{cite web|title=The "Hand" Measurement for Horses|url=http://www.omafra.gov.on.ca/english/livestock/horses/facts/info_hands.htm|publisher=Ministry of Agriculture, Food and Rural Affairs, Ontario, Canada|access-date=30 June 2011 |archive-url=https://web.archive.org/web/20110822161506/http://www.omafra.gov.on.ca/english/livestock/horses/facts/info_hands.htm|archive-date=22 August 2011}}</ref>

===Light-nanosecond===
[[File:Grace Murray Hopper visualizing nanoseconds.png|thumb|Grace Hopper distributed lengths of wire approximately 1 light-nanosecond long in lectures, to remind students not to waste nanoseconds]]
The light-nanosecond is defined as exactly 29.9792458&nbsp;cm. It was popularized in [[Engineering:Information technology|information technology]] as a unit of distance by [[Biography:Grace Hopper|Grace Hopper]] as the distance which a photon could travel in one billionth of a second (roughly 30&nbsp;cm or one foot): "The [[Physics:Speed of light|speed of light]] is one foot per nanosecond."<ref>{{cite web |url=http://cs-www.cs.yale.edu/homes/tap/Files/hopper-story.html |title=Rear Admiral Grace Murray Hopper|date=4 May 2006 |publisher=US Navy}}</ref><ref>{{Cite web|url=https://americanhistory.si.edu/collections/search/object/nmah_692464|title=Nanoseconds Associated with Grace Hopper|website=National Museum of American History}}</ref>

===Metric feet===

A metric foot, defined as {{convert|300|mm|in|3|abbr=off|disp=x| (approximately }}), has been used occasionally in the UK but has never been an official unit.<ref>{{cite web | title=BBC TV Centre | website=History of Television Studios in London | url=https://www.tvstudiohistory.co.uk/studio-category/bbc-tv-centre/ | quote=Measurements are in metric feet (30cm)...}}</ref>

A [[Chi (unit)|Chinese foot]] is around one third of a metre, with the exact definition depending on jurisdiction.

===Horse===
{{main|Horse length}}
Horses are used to measure distances in horse racing – a ''horse length'' (shortened to merely a ''length'' when the context makes it obvious) equals roughly {{convert|8|ft|m|1|abbr=off|disp=or}}. Shorter distances are measured in fractions of a ''horse length''; also common are measurements of a full or fraction of a ''head'', a ''neck'', or a ''nose''.<ref>{{cite web | title=Horse Racing Spread Betting – Get Started | website=Spreadex | url=https://www.spreadex.com/sports/get-started/horse-racing-spread-betting/winning-distances/ | access-date=10 August 2019}}</ref>

===Boat length===
In rowing races such as the Oxford and Cambridge Boat Race, the margin of victory and of defeat is expressed in fractions and multiples of ''boat lengths''. The length of a rowing eight is about {{convert|62|ft|m}}. A shorter distance is the ''canvas'', which is the length of the covered part of the boat between the bow and the bow oarsman. The Racing Rules of Sailing also makes heavy use of boat lengths.

===Football field (length)===
<!--American football field (unit) redirects here. If you change the section heading please update the redirect
-->A football field is often used as a comparative measurement of length when talking about distances that may be hard to comprehend when stated in terms of standard units.

An American football field is usually understood to be {{convert|100|yd|m}} long, though it is technically {{convert|120|yd|m}} when including the two {{convert|10|yd|m|adj=on|abbr=on}} long end zones. The field is {{convert|160|ft|yd m|abbr=on}} wide.<ref>{{Cite web|url=http://operations.nfl.com/the-rules/2015-nfl-rulebook#rule-1.-the-field |archive-url=https://web.archive.org/web/20150824155322/http://operations.nfl.com/the-rules/2015-nfl-rulebook |archive-date=2015-08-24 |title=2015 NFL Rulebook |website=NFL Football Operations}}</ref>

An association football pitch may vary within limits of {{convert|90|-|120|m|yd|abbr=on}} in length and {{convert|45|-|90|m|yd|abbr=on|sigfig=2}} in width. The recommended field size is {{convert|105|x|68|m|yd|abbr=on}} for major competitions such as the FIFA World Cup, UEFA European Championship and UEFA Champions League.

A Canadian football field is {{convert|65|yd|m|abbr=on}} wide and {{convert|150|yd|m|abbr=on}} long, including two {{convert|20|yd|m|adj=on|abbr=on}} long end zones.

===Block===
In most US cities, a [[Engineering:City block|city block]] is between {{convert|1/16|and|1/8|mi|m|abbr=on}}. In Manhattan, the measurement "block" usually refers to a north–south block, which is {{convert|1/20|mi|m|abbr=on}}. Sometimes people living in places (like Manhattan) with a regularly spaced street grid will speak of ''long blocks'' and ''short blocks''. Within a typical large North American city, it is often only possible to travel along east–west and north–south streets, so travel distance between two points is often given in the number of blocks east–west plus the number north–south (known to mathematicians as the ''[[Taxicab geometry|Manhattan Metric]]'').<ref>{{Cite web|url=https://xlinux.nist.gov/dads/HTML/manhattanDistance.html|title=Manhattan distance|website=xlinux.nist.gov}}</ref>

===Earth radius===
The globally-average [[Astronomy:Earth radius|radius of Earth]], generally given as 6,371&nbsp;kilometres (3,959&nbsp;miles), is often employed as a unit of measure to intuitively compare objects of planetary size.

===Lunar distance===
[[Astronomy:Lunar distance|Lunar distance]] (LD), the distance from the centre of Earth to the centre of the Moon, is a unit of measure in astronomy. The lunar distance is approximately {{cvt|384,400|km|mi}}, or 1.28 [[Astronomy:Light-second|light-second]]s; this is roughly 30 times [[Astronomy:Earth radius|Earth's diameter]]. A little less than 400 lunar distances make up an [[Astronomy:Astronomical unit|astronomical unit]].

===Siriometer===
The [[Siriometer|siriometer]] is an obsolete astronomical measure equal to one million [[Astronomy:Astronomical unit|astronomical unit]]s, i.e., one million times the average distance between the Sun and Earth.<ref name=charlier>{{cite book|last1=Charlier|first1=C. V. L.|title=Lectures on Stellar Statistics|year=1921|url=https://www.gutenberg.org/files/22157/22157-h/22157-h.htm|bibcode=1921lss..book.....C}}</ref> This distance is equal to about 15.8&nbsp;[[Astronomy:Light-year|light-year]]s, 149.6&nbsp;[[Peta-|P]]m, or 4.8&nbsp;[[Astronomy:Parsec|parsec]]s, and is about twice the distance from Earth to the star [[Astronomy:Sirius|Sirius]].<!--Google test prefers US spelling--><ref name=beech>{{cite journal|last1=Beech|first1=Martin|title=The reluctant parsec and the overlooked light-year|journal=The Observatory|volume=128|page=489|year=2008|bibcode=2008Obs...128..489B}}</ref>

===Cubit===
The [[Cubit|cubit]] is, among others, a unit used in the Bible for measuring the size of [[Unsolved:Noah's Ark|Noah's Ark]] and of the [[Engineering:Ark of the Covenant|Ark of the Covenant]]. Cubits of various lengths were used in Antiquity by various peoples, not only the Hebrews. One cubit is originally the length from someone's elbow to the tip of their middle finger; it usually translates to approximately half a metre ±10%, with an ancient Roman cubit being as long as 120&nbsp;cm.

One cubit was equal to 6–7 [[Palm (unit)|palms]], one palm being the width of a hand not including the thumb.

==Area==
<!-- Please keep entries sorted in ascending order of magnitude, smallest first -->

=== Barn ===
{{Main|Physics:Barn (unit)}}
One barn is 10<sup>−28</sup>&nbsp;square metres, about the cross-sectional area of a uranium nucleus. The name probably derives from early neutron-deflection experiments, when the uranium nucleus was described, and the phrases "big as a barn" and "hit a barn door" were used. Barn are typically used for [[Physics:Cross section|cross section]]s in nuclear and particle physics. Additional units include the microbarn (or "outhouse")<ref>{{cite web |url=http://www.nuclearglossary.com/abcs/nuclearglossary_O.html#outhouse |title=An Exceptional Nuclear Glossary |publisher=Nuclearglossary.com |date=25 November 2006 |access-date=8 April 2011 |archive-date=27 June 2016 |archive-url=https://web.archive.org/web/20160627084654/http://www.nuclearglossary.com/abcs/nuclearglossary_O.html#outhouse }}</ref> and the yoctobarn (or "shed").<ref name="Rowlett">{{cite web |author= Russ Rowlett |date= 1 September 2004 |title= Units: S |url= http://www.unc.edu/~rowlett/units/dictS.html |website= How Many? A Dictionary of Units of Measurement |publisher= [[Organization:University of North Carolina at Chapel Hill|University of North Carolina at Chapel Hill]] |access-date= 14 December 2009}}</ref><ref>{{cite book |last=Green|first=Jonathon|title=Dictionary of Jargon|url=https://books.google.com/books?id=P0QOAAAAQAAJ&pg=PA487|access-date=14 December 2009|date=December 1987|publisher=Routledge Kegan & Paul|isbn=978-0-7100-9919-8|page=487}}</ref>

===Brass or square===
One brass is exactly {{convert|100|ft2|sigfig=3}} area (used in measurement of work done or to be done, such as plastering, painting, etc.).  The same word is used, however, for {{convert|100|ft3|sigfig=3}} of estimated or supplied loose material, such as sand, gravel, rubble, etc. This unit is prevalent in the construction industry in {{wipe|India}}.<ref>{{cite web|url=http://gardentia.net/chart/|title=Chart|website=gardentia.net|access-date=1 May 2018}}</ref><ref>{{cite news|url=http://www.business-standard.com/article/economy-policy/mumbai-builders-hit-sand-trap-110021200018_1.html|title=Mumbai builders hit sand trap|first=Sanjay|last=Jog|date=12 February 2010|access-date=1 May 2018|via=Business Standard|newspaper=Business Standard India}}</ref>

The same area is called a ''[[Square (unit)|square]]'' in the construction industry in North America,<ref>{{cite web|url=http://www.p1m.com/um.htm|archive-url=https://web.archive.org/web/20031018185707/http://www.p1m.com/um.htm|archive-date=18 October 2003|title=Units of Measurements|date=18 October 2003|access-date=1 May 2018}}</ref> and was historically used in {{wipe|Australia}} by real estate agents.
A [[Engineering:Roof|roof]]'s area may be calculated in square feet, then converted to squares.

===Cow's grass===
In Ireland, before the 19th century, a "cow's grass" was a measurement used by farmers to indicate the size of their fields. A cow's grass was equal to the amount of land that could produce enough grass to support a cow.<ref>{{cite book |last=Kelly|first=John|title=The Graves are Walking: The Great Famine and Saga of the Irish People|page=15|publisher=Henry Holt & Co.|date=2012}}</ref><ref>{{Cite book|url=https://archive.org/details/lettersoncondit00fostgoog|title=Letters on the Condition of the People of Ireland|last=Foster|first=Thomas Campbell|date=1846|publisher=Chapman and Hall|language=en|quote=The land is not let by the acre, but by what is termed a "cow's grass" — so many "cows' grass" to a farm. A "cow's grass" is a measure of land; usually it means as much mountain grazing-land as will keep a cow during the summer, and as much arable-land as will keep the cow-house in fodder during the winter.|page=[https://archive.org/details/lettersoncondit00fostgoog/page/n151 104]}}</ref>
<!--
No evidence of this can be found (in sources not derived from WP). CN tag is 2.5 years old.

A variation called a "cow field"{{clarify|reason=How big is a cow field, in standard units?|date=April 2016}} is still often used in the Channel Islands, particularly Guernsey, where classified advertisements in the local newspaper (''Guernsey Press'') for land can be seen referring to "A plot of land measuring X cow fields." This is probably still used because an acre of land in Guernsey is rather unusual due to the small size of the island and therefore a cow-field is a more suitable unit of measurement.{{citation needed|date=April 2016}}

-->

===Football field (area)===
[[File:Terrains de polo et de football (US compliant).svg|thumb|140px|On this schema, an association football field is used to help to conceptualize the size of a polo field.]]
A football pitch, or field, can be used as a man-in-the-street unit of area.<ref>{{Cite news|url=http://news.bbc.co.uk/2/hi/africa/6097616.stm|title=Nigerian crash airline grounded|date=30 October 2006|via=news.bbc.co.uk}}</ref><ref>{{Cite news|url=http://news.bbc.co.uk/1/hi/england/hereford/worcs/5215118.stm|title=Grass fire strikes the Malverns|date=25 July 2006|via=news.bbc.co.uk}}</ref> The standard FIFA football pitch for international matches is {{convert|105|m|ft|abbr=on}} long by {{convert|68|m|ft|abbr=on}} wide ({{convert|7140|m2|ha acre|abbr=on|disp=or}}); FIFA allows for a variance of up to {{convert|5|m|ft|abbr=on|1}} in length in either direction and {{convert|7|m|ft|abbr=on|1}} more or {{convert|4|m|ft|abbr=on|1}} less in width (and larger departures if the pitch is not used for international competition), which generally results in the association football pitch generally only being used for [[Order of magnitude|order of magnitude]] comparisons.<ref>{{cite web | title=Goal-line technology put on ice | website=fifa.com | date=8 March 2008 | url=http://www.fifa.com/aboutfifa/federation/bodies/media/newsid%3D707751.html | archive-url=https://web.archive.org/web/20101223112215/http://www.fifa.com/aboutfifa/federation/bodies/media/newsid%3D707751.html | archive-date=23 December 2010 | access-date=10 August 2019}}</ref>

An American football field, including both end zones, is {{convert|360|by|160|ft|yd m|1|abbr=on}}, or {{convert|57600|sqft|m2}} ({{convert|0.535|ha|acre|disp=or}}). A Canadian football field is {{convert|65|yd|m}} wide and {{convert|110|yd|m}} long with end zones adding a combined {{convert|40|yd|m}} to the length, making it {{convert|87750|sqft|m2}} or {{convert|0.8215|ha|acre|abbr=on}}.

An Australian rules football field may be approximately {{convert|150|m|yd}} (or more) long goal to goal and {{convert|135|m|yd}} (or more) wide, although the field's elliptical nature reduces its area to a certain extent. A {{convert|150|by|135|m|yd|adj=on}} football field has an area of approximately {{convert|15900|m2|ha acre|abbr=on}}, twice the area of a Canadian football field and three times that of an American football field.

===Morgen===
{{Main|Morgen}}
A [[Morgen|morgen]] ("morning" in Dutch and German) was approximately the amount of land tillable by one man behind an ox in the morning hours of a day. This was an official unit of measurement in South Africa until the 1970s, and was defined in November 2007 by the South African Law Society as having a conversion factor of 1&nbsp;morgen = {{val|0.856532|u=hectare}}.<ref>{{cite web
|url= http://www.lawsoc.co.za/webs/surveyorgeneral/2007_11_area_conversion.doc
|title= Instructions for the Conversions of Areas to Metric
|publisher= Law Society of South Africa
|date= November 2007
|access-date= 27 December 2013
|archive-date= 20 March 2018
|archive-url= https://web.archive.org/web/20180320105433/https://www.lawsoc.co.za/webs/surveyorgeneral/2007_11_area_conversion.doc
}}</ref> This unit of measure was also used in the Dutch colonial province of New Netherland (later New York and parts of New England).<ref>{{cite book|last=O'Callaghan|first=Edmund Bailey |title=Laws and Ordinances of New Netherland, 1638–1674|url=https://archive.org/details/cu31924080779402|year=1868|publisher=Weed, Parsons, printers|location=Albany, NY|page=[https://archive.org/details/cu31924080779402/page/n372 335]}}</ref><ref>{{cite web|url=http://www.rootsweb.ancestry.com/~nycoloni/nnlandex.html,|title=RootsWeb.com Home Page|website=www.rootsweb.ancestry.com|access-date=1 May 2018|archive-url=https://web.archive.org/web/20180501133050/http://www.rootsweb.ancestry.com/~nycoloni/nnlandex.html,|archive-date=1 May 2018}}</ref>

===Countries, regions, and cities===
The area of a familiar country, state or city is often used as a unit of measure, especially in journalism.

====Wales====
[[File:British Isles United Kingdom WA highlighted.svg|thumb|upright|Wales (red) in the UK (pink)]]Equal to 20,779&nbsp;km<sup>2</sup> (8,023&nbsp;sq&nbsp;mi), the country of Wales is used in phrases such as "an area the size of Wales"<ref>{{cite news|url=https://www.bbc.co.uk/news/uk-wales-46737277 |title=Why is Wales used as a unit of measurement? |newspaper=BBC News |access-date=22 January 2019|date=22 January 2019 |last1=Frampton |first1=Ben }}</ref> or "twice the area of Wales".<ref>{{Cite news|url=http://news.bbc.co.uk/1/hi/wales/south_west/4543070.stm|title=Expat joins Falklands council|date=24 December 2005|via=news.bbc.co.uk}}</ref><ref>{{Cite news|url=http://news.bbc.co.uk/2/hi/science/nature/5184332.stm|title=Diary: The Amazon rainforest|date=19 July 2006|via=news.bbc.co.uk}}</ref> {{wipe|England}} is 6.275 times the size of Wales, and Scotland is roughly four times the size of Wales. Ireland is four times as large as Wales, and {{wipe|France}} is about twenty-five times larger.

The British comedy show ''The Eleven O'Clock Show'' parodied the use of this measurement, by introducing a news article about an earthquake in Wales, stating that an area the size of Wales was affected. The Radio 4 programme ''More or Less'' introduced the idea of "kilowales"&nbsp;– an area 1,000 times the size of Wales. ''The Register'' introduced the nanowales (20.78&nbsp;m<sup>2</sup>).<ref>{{cite web |last=Haines|first=Lester|title=So, what's the velocity of a sheep in a vacuum?|url=https://www.theregister.co.uk/2007/08/24/vulture_central_standards/?page=2|archive-url=https://web.archive.org/web/20131114110120/https://www.theregister.co.uk/2007/08/24/vulture_central_standards/?page=2|archive-date=14 November 2013|website=The Register|date=24 August 2007|access-date=25 August 2015}}</ref>

The measurement has been adopted by rainforest conservation charity [[Organization:Size of Wales|Size of Wales]], aiming to conserve an area of rainforest equating to the area of Wales. On 1 March 2013, the [[Organization:Charitable organization|charity]] announced that they had succeeded<ref>{{cite web |title=What next for Size of Wales?|url=http://sizeofwales.tumblr.com/post/57366552318/whats-next-for-size-of-wales|publisher=Size of Wales|access-date=31 May 2014}}</ref> in conserving an area of rainforest the size of Wales and will continue to operate to sustain and increase the protected area.<ref>{{cite news |last=Vaughn|first=Adam|title=Welsh charity saves an area of rainforest the size of Wales|url=https://www.theguardian.com/environment/2013/mar/01/charity-saves-rainforest-size-of-wales|access-date=31 May 2014|newspaper=Guardian|date=1 March 2013}}</ref>

====United States====
In the United States, the area of the smallest state, Rhode Island ({{convert|1545|sqmi|km2|disp=or|abbr=on}}); the largest of the contiguous 48 states, {{wipe|Texas}} ({{convert|268601|sqmi|km2|disp=or|abbr=on}}); and less commonly [[Earth:Alaska|Alaska]] ({{convert|656425|sqmi|km2|disp=or|abbr=on}}), the largest of all 50&nbsp;states, are used in a similar fashion. For example, [[Earth:Antarctica|Antarctica]]'s [[Earth:Larsen Ice Shelf|Larsen B ice shelf]] was approximately the size of Rhode Island until it broke up in 2002. Other areas may be described like this, too, like in the 1979 movie ''The China Syndrome'' when radiation is expected to contaminate "an area the size of Pennsylvania".

The US Central Intelligence Agency uses [[Place:Washington, D.C.|Washington, D.C.]] ({{convert|61.4|sqmi|km2|disp=or|abbr=on}}) as a comparison for city-sized objects.{{Citation needed|date=March 2011}}

====Other countries====
In the Netherlands, its smallest province, Utrecht ({{convert|1386|km2|sqmi|abbr=on|disp=or}}), is often used as a comparison for regions in general.

The country of Belgium ({{convert|30528|km2|sqmi|disp=or|abbr=on}}) has also often been used when comparing areas, to the point where it has been regarded as a [[Philosophy:Meme|meme]]<ref>{{cite news|first=Chris |last=Edwards |title=Quizzical: this month, Chris Edwards tackles temperature extremes, the size of Belgium, categorising nations' development status, the hydrogen bombs dropped on Japan and the number of people who speak Scottish Gaelic |url=http://findarticles.com/p/articles/mi_hb3120/is_8_77/ai_n29198390/ |work=Geographical |date=August 2005 |access-date=20 May 2009 |archive-url=https://web.archive.org/web/20110413081725/http://findarticles.com/p/articles/mi_hb3120/is_8_77/ai_n29198390/ |archive-date=13 April 2011 }}</ref> and where there is a [http://www.sizeofbelgium.com/ website] dedicated to notable areas which have been compared to that of Belgium.

The Isle of Wight ({{convert|380|km2|sqmi|0|disp=or|abbr=on}}), an island off the south coast of mainland {{wipe|England}}, is commonly used to define smaller areas. It has sometimes been used in attempts to examine whether a certain amount of a given object or group would fit in a space its size; in 2018, it was estimated that approximately 2.6&nbsp;billion people could fit on the Isle of Wight, at a population density of six people per square metre.<ref>{{cite web |last1=White |first1=Jamie |title=Would The World's Population Fit on the Isle of Wight? |url=https://iwradio.co.uk/2018/03/08/worlds-population-fit-isle-wight/ |website=Isle of Wight Radio|date=8 March 2018 }}</ref>

In {{wipe|Denmark}}, the outlying island of Bornholm ({{convert|588|km2|abbr=on|disp=or}}) is often used to describe the size of an area.

In Germany, the state of Saarland ({{convert|2569.69|km2|sqmi|disp=or|abbr=on}}) is often used to define areas.<ref>{{cite news |url=https://www.welt.de/wissenschaft/article6452153/Das-Saarland-das-Vergleichsmass-vieler-Dinge.html|title=Größenordnungen: Das Saarland – das Vergleichsmaß vieler Dinge – DIE WELT|author=Marco Krefting|date=18 February 2010|newspaper=DIE WELT}}</ref>

In {{wipe|Brazil}}, it is common to compare relatively small areas to the state of Sergipe ({{convert|21910.4|km2|sqmi|disp=or|abbr=on}}), the smallest in the country. Smaller areas are sometimes compared to the cities of São Paulo ({{convert|1521.11|km2|sqmi|disp=or|abbr=on}}) or Rio de Janeiro ({{convert|1221|km2|sqmi|disp=or|abbr=on}}).

==Volume==
<!-- Please keep entries sorted in ascending order of magnitude, smallest first -->

===Metric ounce===
A metric ounce is an approximation of the imperial ounce, US dry ounce, or US fluid ounce. These three customary units vary. However, the metric ounce is usually taken as 25 or 30&nbsp;ml when volume is being measured, or grams when mass is being measured.

The US [[Organization:Food and Drug Administration|Food and Drug Administration]] (FDA) defines the "food labeling ounce" as 30&nbsp;ml, slightly larger than the 29.6&nbsp;ml [[Fluid ounce|fluid ounce]].<ref>{{cite web |url=http://edocket.access.gpo.gov/cfr_2004/aprqtr/21cfr101.9.htm |title=Food and Drugs: FDA Food Labeling |date=1 April 2004 |publisher=US Government Printing Office |access-date=27 August 2012 |archive-url=https://web.archive.org/web/20120204081321/http://edocket.access.gpo.gov/cfr_2004/aprqtr/21cfr101.9.htm |archive-date=4 February 2012 }}<br />For Nutrition facts labeling "a teaspoon means 5 milliliters (ml), a tablespoon means 15 ml, a cup means 240 ml, 1 fl oz means 30 ml, and 1 oz in weight means 28 g".</ref>

Several [[Physics:Dutch units of measurement|Dutch units of measurement]] have been replaced with informal metric equivalents, including the ''ons'' or ounce. It originally meant {{Fraction|1|16}} of a pound, or a little over 30&nbsp;grams depending on which definition of the pound was used, but was redefined as 100&nbsp;grams when the country metricated.<ref>{{Cite web|url=https://hollandexpatcenter.com/en/living-in/practical-information/|title=Practical information|website=Holland Expat Center}}</ref>

===Shot===
{{Main|Shot glass}}
[[File:Three shotglasses.jpg|thumb|right|Three shot glasses of varying shape and size]]
The [[Shot glass|shot]] is a liquid volume measure that varies from country to country and state to state depending on legislation. It is routinely used for measuring strong [[Chemistry:Liquor|liquor]] or spirits when the amount served and consumed is smaller than the more common measures of alcoholic "drink" and "pint". There is a legally defined maximum size of a serving in some jurisdictions. The size of a "single" shot is {{convert|20|-|60|ml|abbr=on}}. The smaller "pony" shot is {{convert|20|-|30|ml|abbr=on}}. According to Encyclopædia Britannica Almanac 2009, a pony is 0.75 [[Fluid ounce|fluid ounce]]s{{clarify|date=September 2014|reason=Imperial fluid ounces, US fluid ounces, or something else?}} of liquor.<ref name="BritannicaAlmanac">{{cite book |title=Encyclopaedia Britannica Almanac 2009|date=2009|publisher=Encyclopædia Britannica|isbn=978-1-59339-839-2|page=160|url=https://books.google.com/books?id=2nxLkMspauIC&pg=PA160|editor=Encyclopædia Britannica Inc. Staff |access-date=22 April 2013}}</ref> According to [[Physics:Wolfram Alpha|Wolfram Alpha]], one pony is 1&nbsp;U.S. fluid ounce.<ref name="WA Pony">{{cite web |url=http://www.wolframalpha.com/input/?i=what+is+one+pony |title=what is one pony |publisher=Wolfram Alpha |date=19 June 2014 |access-date=19 June 2014}}</ref><!-- Site gives conversion as 19.57 cm3, which equals 1 US fl oz--> "Double" shots (surprisingly not always the size of two single shots, even in the same place) are {{convert|40|-|100|ml|abbr=on}}. In the UK, spirits are sold in shots of either 25&nbsp;ml (approximating the old [[Fluid ounce|fluid ounce]]) or 35&nbsp;ml.<ref>{{Cite web|url=https://www.gov.uk/weights-measures-and-packaging-the-law/specified-quantities|title=Weights and measures: the law|website=GOV.UK}}</ref>

===Board foot or super foot===
{{Main|Board foot}}
A board foot is a United States and Canadian unit of approximate volume, used for lumber. It is equivalent to {{nowrap|1 inch × 1 foot × 1 foot}} ({{convert|144|cuin|0|disp=or|abbr=on}}). It is also found in the unit of density ''pounds per board foot''. In Australia and New Zealand the terms ''super foot'' or ''superficial foot'' were formerly used for this unit. The exact volume of wood specified is variable and depends on the type of lumber. For planed lumber the dimensions used to calculate board feet are [[Real versus nominal value|nominal dimensions]], which are larger than the actual size of the planed boards. See Dimensional lumber for more information on this.

===Hoppus foot===
{{further|Hoppus}}
A system of measure for timber in the round (standing or felled), now largely superseded by the metric system except in measuring hardwoods in certain countries. Its purpose is to estimate the value of sawn timber in a log, by measuring the unsawn log and allowing for wastage in the mill. Following the so-called "quarter-girth formula" (the square of one quarter of the circumference in inches multiplied by {{frac|1|144}} of the length in feet), the notional log is four feet in circumference, one inch of which yields the hoppus board foot, 1&nbsp;foot yields the hoppus foot, and 50&nbsp;feet yields a hoppus ton. This translates to a hoppus foot being equal to {{convert|1.273|ft3|in3 m3}}. The hoppus board foot, when milled, yields about one [[Board foot|board foot]]. The volume yielded by the quarter-girth formula is 78.54% of cubic measure (i.e. 1&nbsp;ft<sup>3</sup> = 0.7854&nbsp;h&nbsp;ft; 1&nbsp;h&nbsp;ft = 1.273&nbsp;ft<sup>3</sup>).<ref name="forest mensuration">{{cite book |last= Husch |first= Bertram |author2=Thomas W. Beers |author3=John A. Kershaw |title= Forest Mensuration |url=https://books.google.com/books?id=p0v3m8Pau-kC&pg=PA202|publisher= John Wiley and Sons |date= 2003 |isbn= 978-0-471-01850-6}}</ref>

===Cubic ton===
{{Main|Physics:Cubic ton}}
A cubic ton is an antiquated measure of volume, varying based on the commodity from about {{convert|16|to|45|ft3|m3|abbr=on}}. It is now only used for lumber, for which one cubic ton is equivalent to {{convert|40|ft3|m3|abbr=on}}.

===Cord and rick===
[[File:Cord of wood.jpg|thumb|A cord of wood]]
{{Main|Cord (unit)}}
The cord is a unit of measure of [[Physics:Dry measure|dry volume]] used in Canada and the United States to measure firewood and pulpwood. A cord is the amount of wood that, when "ranked and well stowed" (arranged so pieces are aligned, parallel, touching and compact), occupies a volume of {{convert|128|cuft|m3|2}}.<ref>{{cite web |author=British Columbia Ministry of Forests and Range|title=Glossary of Forestry Terms in British Columbia|url=http://www.for.gov.bc.ca/hfd/library/documents/glossary/Glossary.pdf|access-date=4 September 2008}}</ref> This corresponds to a well-stacked woodpile, 4&nbsp;feet deep by 4&nbsp;feet high by 8&nbsp;feet wide {{nowrap|(122 cm × 122&nbsp;cm × 244&nbsp;cm)}}, or any other arrangement of linear measurements that yields the same volume. A more unusual measurement for firewood is the "rick" or [[Face cord|face cord]]. It is stacked {{convert|16|in|cm|sigfig=3}} deep with the other measurements kept the same as a cord, making it {{frac|3}} of a cord; however, regional variations mean that its precise definition is non-standardized.<ref>{{cite web|url=http://www.ibiblio.org/units/dictR.html|title=Units: R|last=Rowlett|first=Russ|date=25 April 2002|website=How Many? A Dictionary of Units of Measurement|access-date=10 August 2019}}</ref>

===Twenty-foot equivalent unit===
{{main|Twenty-foot equivalent unit}}
The twenty-foot equivalent unit is the volume of the smallest standard [[Engineering:Intermodal container|shipping container]]. It is equivalent to {{convert|1360|cuft|m3}}. Larger intermodal containers are commonly described in multiples of TEU, as are container ship capacities.

===Acre-foot===
{{Main|Acre-foot}}
An acre-foot is a unit of volume commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, irrigation water<ref>{{cite web |title=NM OSE Glossary|url=http://www.ose.state.nm.us/water_info_glossary.html#A|archive-url=https://web.archive.org/web/20051114202301/http://www.ose.state.nm.us/water_info_glossary.html|archive-date=14 November 2005|access-date=15 March 2014}}</ref> and river flows. It is defined by the volume of one acre of surface area to a depth of one foot. {{convert|43560|ft3|m3 USgal impgal|0|abbr=on}}.

===Casual units===
Many well-known objects are regularly used as casual units of volume. They include:

;Double-decker bus: The approximate volume of a [[Engineering:Double-decker bus|double-decker bus]], abbreviated to DDB, has been used informally to describe the size of hole created by a major sewer collapse. For example, a report might refer to "a 4 DDB hole".<ref>{{cite book |url=https://books.google.com/books?id=8wpnoExCJOcC|title=Sewers: Repair and Renovation|publisher= Butterworth-Heinemann |editor=Geoffrey F Read |editor2=Ian Vickridge |date=24 December 1996|access-date=29 June 2016|isbn=978-0-08-054112-9}}</ref>

;Olympic-size swimming pool: [[File:Olympic Swimming Pool - Fast Lane.JPG|thumb|An Olympic-size swimming pool holds over 2&nbsp;acre-feet of water]] For larger volumes of liquid, one measure commonly used in the media in many countries is the Olympic-size swimming pool.<ref>Paul Hudson: [https://www.bbc.co.uk/blogs/paulhudson/2010/06/3rd-anniversary-of-july-2007-f.shtml 3rd anniversary of June 2007 floods], showing a storm water storage tank "half the size of an Olympic swimming pool"</ref> A {{convert|50|×|25|m|abbr=on}} Olympic swimming pool, built to the FR3 minimum depth of {{convert|2|m|ft|1}} would hold {{convert|2500|m3|l impgal USgal acre·ft|abbr=on}}. The US [[Organization:National Institute of Standards and Technology|National Institute of Standards and Technology]] (NIST) defines the Olympic swimming pool as 1&nbsp;million litres, which is the approximate volume of the smaller FR2 pool.<ref>{{cite web|url=https://www.nist.gov/pml/wmd/metric/volume.cfm|title=SI Units – Volume|first=Isabel|last=Chavez|date=1 August 2011|website=nist.gov|access-date=1 May 2018}}</ref>

;Royal Albert Hall: The Royal Albert Hall, a large concert hall, is sometimes used as a unit of volume in the UK, for example when referring to volumes of rubbish placed in landfill.<ref>p [http://news.bbc.co.uk/1/hi/uk/7949761.stm "Landfill tax 'costing homes £30'", BBC News website]</ref> It is famously used in the line "Now they know how many holes it takes to fill the Albert Hall." in The Beatles song "A Day in the Life".<ref name="Origins">{{cite web |url=http://www.applecorp.com/aditl/origins.htm |title=A Day in the Life&nbsp;– An Indepth Analysis&nbsp;– The Origins of the Song |access-date=18 September 2010 |archive-url= https://web.archive.org/web/20080419020720/http://www.applecorp.com/aditl/origins.htm |archive-date= 19 April 2008}}</ref> The volume of the auditorium is between 3 and 3.5&nbsp;million cubic feet (between 85,000 and 99,000 cubic metres).<ref>{{cite book
|last=Atwood|first=Robert
|date=2006
|title=Bears Can't Run Downhill, and 200 Dubious Pub Facts Explained
|publisher=Ebury Press
|page=124
|isbn=978-0-09-191255-0
}}</ref>

;Melbourne Cricket Ground: A common measure of volume in {{wipe|Australia}}, and in the state of Victoria in particular, is the Melbourne Cricket Ground, the largest stadium in Australia and 13th largest in the world.<ref>{{cite web |url=http://www.theage.com.au/articles/2003/12/05/1070351787509.html |title=Trouble brewing at the bottom of the bay |author= The Age |access-date=4 September 2014|date=6 December 2003 }}</ref> The volume of the Melbourne Cricket Ground is 1,574,000 cubic metres, or about 630&nbsp;Olympic swimming pools.<ref>{{cite web |url=http://www.abc.net.au/news/2015-08-20/surveyors-find-exact-measurements-of-melbourne-cricket-ground/6709520 |title=How big is the MCG? Surveyors find exact measurements of Melbourne Cricket Ground|publisher=Australian Broadcasting Corporation|author=Margaret Paul|date=20 August 2015|access-date=20 August 2015}}</ref> Its seating capacity (100,000 {{as of|July 2019|lc=y}}) is also used as a unit measure of the number of people.

;{{visible anchor|Sydney Harbour}}: [[File:Sydney(from air) V2.jpg|thumb|Sydney Harbour (Port Jackson)]] A unit of volume used in Australia for water. One Sydney Harbour is the amount of water in Sydney Harbour: approximately 562&nbsp;gigalitres (562,000,000 cubic metres, or 0.562 of a cubic [[Kilometre|kilometre]]); or in terms of the more unusual measures above, about 357&nbsp;Melbourne Cricket Grounds, 238,000&nbsp;Olympic Swimming pools, or 476,000&nbsp;acre-feet.<ref>{{cite web |url=http://www.smh.com.au/news/National/The-secret-harbour-uncovered/2004/12/10/1102625541209.html|archive-url=https://web.archive.org/web/20160116134156/http://www.smh.com.au/news/National/The-secret-harbour-uncovered/2004/12/10/1102625541209.html|title=The secret harbour uncovered|archive-date=16 January 2016|date=11 December 2004}}</ref><ref>{{cite web |url=http://media.bom.gov.au/social/blog/39/when-dam-size-matters/ |title=When dam size matters |author= Australian Bureau of Meteorology |access-date=4 September 2014}}</ref><ref>{{cite web |author=NSW Irrigators' Council (NSWIC)|title=Useful Water Comparisons|url=http://www.nswic.org.au/pdf/fact_sheets/USEFUL%20WATER%20COMPARISONS.pdf|access-date=4 September 2014}}</ref>

;The Grand Canyon: With a volume measure approximately 4 orders of magnitude greater than Sydney Harbour, the volume of the [[Earth:Grand Canyon|Grand Canyon]] may be used to visualize even larger things, like the magma chamber underneath Yellowstone<ref>{{cite news |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2015/04/23/scientists-find-missing-link-in-yellowstone-plumbing-this-giant-volcano-is-very-much-alive/|title=Scientists find missing link in Yellowstone plumbing: This giant volcano is very much alive|author=Joel Achenbach|date=23 April 2015|newspaper=Washington Post}}</ref> and other things.<ref>{{cite AV media|url=https://www.youtube.com/watch?v=C6eOcd06kdk| archive-url=https://ghostarchive.org/varchive/youtube/20211117/C6eOcd06kdk| archive-date=2021-11-17 | url-status=live|title=How Many Things Are There?|date=28 April 2014|via=YouTube}}{{cbignore}}</ref><ref>{{Cite web|url=http://eesmyal.com/2012/02/human-cube/|title=Human Cube – eesmyal}}</ref> According to the National Park Service, the volume of the Grand Canyon is {{convert|4.17|e12m3|e12yd3|abbr=off}}<ref>{{Cite web|url=https://www.nps.gov/grca/learn/management/statistics.htm|title=Park Statistics - Grand Canyon National Park (U.S. National Park Service)|website=www.nps.gov}}</ref> which is {{convert|4.17|e12m3|km3|disp=output only}} ({{convert|4.17|e12m3|mi3|disp=output only}}).

==Flow rate==
===Miner's inch===
{{main|Physics:Miner's inch}}
The volume of water which flows in one unit of time through an orifice of one square inch area. The size of the unit varies from one place to another.

==Mass==

<!-- Please keep entries sorted in ascending order of magnitude, smallest first -->

=== Electronvolt mass ===
It is common in particle physics to use eV/''c''<sup>2</sup> as a unit of mass. Here, eV (electronvolt) is a unit of energy (the kinetic energy of an [[Physics:Electron|electron]] accelerated over one [[Volt|volt]], {{val|1.6|e=-19}}&nbsp;[[Joule|joule]]s), and ''c'' is the speed of light in vacuum. Energy and mass are related through ''E''&nbsp;=&nbsp;''mc''<sup>2</sup>. This definition is useful for a [[Physics:Linear particle accelerator|linear particle accelerator]] when accelerating electrons.

{{block indent | text = 1 [[Dalton (unit)|dalton]]&nbsp;= 931.46 MeV/''c''<sup>2</sup>}}

In many systems of [[Natural units|natural units]] {{nowrap|1=''c'' = 1}}, so the ''c'' is dropped and eV itself becomes a unit of mass.

=== Bag of cement and bag mix ===
The mass of an old bag of cement was one [[Hundredweight|hundredweight]] ({{convert|112|lb|disp=comma}}). The amount of material that an aircraft could carry into the air is often visualised as the number of bags of cement that it could lift.{{Citation needed|date=March 2023}} In the concrete and petroleum industry, however, a bag of cement is defined as {{cvt|94|lb}} because it has an apparent volume close to {{convert|1|cuft|litre|abbr=off}}.<ref>{{cite web |url=http://www.cement.org/tech/faq_unit_weights.asp|title=Frequently Asked Questions, unit weights|publisher=Portland Cement Association|date=2011|access-date=15 February 2011}}</ref> When [[Engineering:Ready-mix concrete|ready-mix concrete]] is specified, a "bag mix" unit is used as if the batching company mixes 5 literal bags of cement per cubic yard (or cubic metre) when a "5&nbsp;bag mix" is ordered.{{Citation needed|date=April 2020|reason==cubic yard is significantly different from cubic meter}}

===Grave===
In 1793, the French term "[[Grave (unit)|grave]]" (from "gravity") was suggested as the base unit of mass for the metric system. In 1795, however, the name "kilogramme" was adopted instead.

===Jupiter===
[[File:Jupiter,_image_taken_by_NASA%27s_Hubble_Space_Telescope,_June_2019_-_Edited.jpg|thumb|upright|Jupiter]]
When reporting on the masses of extrasolar planets, astronomers often discuss them in terms of multiples of [[Astronomy:Jupiter mass|Jupiter's mass]] ({{Jupiter mass}} = 1.9 {{e|27}}&nbsp;kg).<ref>{{cite news |url=http://www.space.com/scienceastronomy/extrasolar-planet-types-100214.html |title=Out There: A Strange Zoo of Other Worlds |work=Space.com |date=14 February 2010}}</ref> For example, "Astronomers recently discovered a planet outside our Solar System with a mass of approximately 3&nbsp;Jupiters." Furthermore, the mass of Jupiter is nearly equal to one thousandth of the mass of the Sun.

===Sun===
[[Astronomy:Solar mass|Solar mass]] ({{Solar mass}} = {{val|2.0|e=30|u=kg}}) is also often used in astronomy when talking about masses of stars or galaxies; for example, Alpha Centauri A has the mass of 1.1&nbsp;suns, and the [[Astronomy:Milky Way|Milky Way]] has a mass of approximately {{Solar mass|6{{e|11}}}}.

Solar mass also has a special use when estimating orbital periods and distances of 2 bodies using Kepler's laws: ''a<sup>3</sup> = M<sub>total</sub>T<sup>2</sup>'', where ''a'' is length of semi-major axis in [[Astronomy:Astronomical unit|AU]], ''T'' is orbital period in years and ''M<sub>total</sub>'' is the combined mass of objects in {{Solar mass}}. In case of planet orbiting a star, ''M<sub>total</sub>'' can be approximated to mean the mass of the central object. More specifically in the case of Sun and Earth the numbers reduce to ''M<sub>total</sub>'' ~ 1, ''a'' ~ 1 and ''T'' ~ 1.

==Time==
<!-- Please keep entries sorted in ascending order of magnitude, smallest first -->

===Light-distance===
[[Biography:George Gamow|George Gamow]] discussed measurements of time such as the "light-mile" and "light-foot", the time taken for light to travel the specified unit distance, defined by "reversing the procedure" used in defining a light-year.<ref>{{cite book |author=George Gamow|title=One Two Three ... Infinity: Facts and Speculations of Science|location=New York|publisher=Viking|date=1947|page=77|title-link=One Two Three ... Infinity}}</ref> A light-foot is roughly one [[Nanosecond|nanosecond]].<ref>[[Biography:N. David Mermin|N. David Mermin]] (2005) ''It's About Time'', page 22</ref>

===Shake===
In [[Physics:Nuclear chain reaction|nuclear engineering]] and astrophysics contexts, the shake is sometimes used as a conveniently short period of time. 1&nbsp;shake is defined as 10&nbsp;[[Nanosecond|nanosecond]]s.<ref>{{cite web|title=The Pathogenesis and Therapy of Combined Radiation Injury |url=http://www.afrri.usuhs.mil/www/outreach/pdf/CR06_1.pdf |archive-url=https://web.archive.org/web/20070106134035/http://www.afrri.usuhs.mil/www/outreach/pdf/CR06_1.pdf |archive-date=6 January 2007 |publisher=Defense Threat Reduction Agency |access-date=12 November 2006 }}</ref>

===Jiffy===
In [[Computing|computing]], the [[Jiffy (time)|jiffy]] is the duration of one tick of the system timer [[Interrupt|interrupt]]. Typically, this time is 0.01&nbsp;seconds, though in some earlier systems (such as the [[Company:Commodore International|Commodore]] [[8-bit|8-bit]] machines) the jiffy was defined as {{frac|1|60}} of a second, roughly equal to the vertical refresh period (i.e. the field rate) on [[Engineering:NTSC|NTSC]] video hardware (and the [[Physics:Utility frequency|period of AC electric power]] in North America).

===Microfortnight===
One unit derived from the [[Physics:FFF system|FFF system]] of units is the microfortnight, one millionth of the fundamental time unit of FFF, which equals 1.2096&nbsp;seconds. This is a fairly representative example of "hacker humor",<ref>{{Cite web|url=http://catb.org/jargon/html/M/microfortnight.html|title=microfortnight|website=catb.org}}</ref> and is occasionally used in operating systems; for example, the [[Software:OpenVMS|OpenVMS]] TIMEPROMPTWAIT parameter is measured in microfortnights.<ref>{{cite web |url=http://www.faqs.org/faqs/dec-faq/vms/part3 |title=OpenVMS Frequently Asked Questions (FAQ), Part 3/11 |at=4.1.1.1.4 EXE$GL_TODR |date=11 April 2005 |access-date=10 March 2009}}</ref>

===Sidereal day===
The sidereal day is based on the Earth's rotation rate relative to fixed stars, rather than the Sun. A sidereal day is approximately 23&nbsp;hours, 56&nbsp;minutes, 4.0905&nbsp;SI&nbsp;seconds.

===Decimal time systems===
{{main|Decimal time}}
[[File:Decimal_Time_Clock.jpeg|thumb|Decimal Time clock reading 2.50 DT equivalent to 6 AM standard time]]
The measurement of time is unique in SI in that while the [[Second|second]] is the base unit, and measurements of time smaller than a second use prefixed units smaller than a second (e.g. microsecond, nanosecond, etc.), measurements larger than a second instead use traditional divisions, including the [[Sexagesimal|sexagesimal]]-based ''[[Minute|minute]]'' and ''[[Hour|hour]]'' as well as the less regular ''[[Day|day]]'' and ''[[Year|year]]'' units.

SI allows for the use of larger prefixed units based on the second, a system known as [[Metric time|metric time]], but this is seldom used, since the number of seconds in a day (86,400 or, in rare cases, 86,401) negate one of the metric system's primary advantages: easy conversion by multiplying or dividing by powers of ten.

There have been numerous proposals and usage of [[Decimal time|decimal time]], most of which were based on the day as the base unit, such that the number of units between any two events that happen at the same time of day would be equal to the number of days between them multiplied by some integer power of ten. In dynastic China, the kè was a unit that represented {{frac|1|100}} of a day (it has since been redefined to {{frac|1|96}} of a day, or 15&nbsp;minutes). In France, a decimal time system in place from 1793 to 1805 divided the day into 10&nbsp;hours, each divided into 100&nbsp;minutes, in turn each divided into 100&nbsp;seconds; the [[French Republican Calendar]] further extended this by assembling days into ten-day "weeks".

[[Ordinal date]]s and [[Astronomy:Julian day|Julian day]]s, the latter of which has seen use in astronomy as it is not subject to [[Physics:Leap year|leap year]] complications, allow for the expression of a decimal portion of the day.<ref>See, for instance, the [http://tycho.usno.navy.mil/cgi-bin/daterdnm.sh current Mean Julian Day] {{Webarchive|url=https://web.archive.org/web/20110606205531/http://tycho.usno.navy.mil/cgi-bin/daterdnm.sh |date=6 June 2011 }}, precise to 6 decimal place, from the United States Naval Observatory.</ref> In the mid-1960s, to defeat the advantage of the recently introduced computers for the then popular rally racing in the Midwest, competition lag times in a few events were given in centids ({{frac|1|100}}&nbsp;day, 864&nbsp;seconds, 14.4&nbsp;minutes), millids ({{frac|1|1,000}}&nbsp;day, 86.4&nbsp;seconds), and centims ({{frac|1|100}}&nbsp;minute, 0.6&nbsp;seconds) the latter two looking and sounding a bit like the related units of minutes and seconds.{{verify source|date=December 2020}} Decimal time proposals are frequently used in fiction, often in [[Social:Futurism|futuristic]] works.

In addition to decimal time, there also exist [[Binary clock|binary clock]]s and [[Hexadecimal time|hexadecimal time]].

The [[Swatch Internet Time]] system is based on Decimal time.

===Sol===
{{main|Astronomy:Sol (day on Mars)}}
{{further|Astronomy:Timekeeping on Mars}}
The United States-based [[Organization:NASA|NASA]], when conducting missions to the planet Mars, has typically used a time of day system calibrated to the mean solar day on that planet (known as a "sol"), training those involved on those missions to acclimate to that length of day, which is 88,775&nbsp;SI&nbsp;seconds, or 2,375&nbsp;seconds (about 39&nbsp;minutes) longer than the mean solar day on Earth. NASA's Martian timekeeping system (instead of breaking down the sol into 25×53×67 or 25×67×53 SI second divisions) slows down clocks so that the 24-hour day is stretched to the length of that on Mars; Martian hours, minutes and seconds are thus 2.75% longer than their SI-compatible counterparts.<ref>{{cite web |url= https://mars.nasa.gov/mer/spotlight/spirit/a3_20040108.html |title=Watchmaker With Time to Lose |website=JPL Mars Exploration Rovers |year=2014 |access-date=22 January 2015}}</ref><ref>{{cite web |url= http://www.space.com/20243-mars-rover-curiosity-discoveries-grotzinger.html |title=After Finding Mars Was Habitable, Curiosity Keeps Roving |first=Nola Taylor |last=Redd |website=space.com |date=18 March 2013 |access-date=22 January 2015}}</ref>

The [[Astronomy:Darian calendar|Darian calendar]] is an arrangement of sols into a Martian year. It maintains a seven-sol week (retaining Sunday through Saturday naming customs), with four weeks to a month and 24&nbsp;months to a Martian year, which contains 668 or 669&nbsp;sols depending on [[Physics:Leap year|leap year]]s. The last Saturday of every six months is skipped over in the Darian calendar.

===Dog year===
[[File:10 yr old Mastiff.JPG|thumb|A 10-year-old Neapolitan Mastiff]]
There are two diametrically opposed definitions of the ''dog year'', primarily used to approximate the equivalent age of [[Biology:Dog|dog]]s and other animals with similar life spans. Both are based upon a popular myth regarding the aging of dogs that states that a dog ages seven years in the time it takes a human to age one year.
*One seventh of a year, or approximately 52&nbsp;days.<ref name=dogyear>[https://web.archive.org/web/20110612143355/http://today.msnbc.msn.com/id/43339983/ns/today-today_pets_and_animals Multimillionaire pooch dies at age 12 (84 in dog years)]. ''MSNBC.com''. Retrieved 12 June 2011.</ref> When this definition is used, a standard calendar year is known as a "human year".
*A standard (365-day) calendar year of a dog's life, whereas a "human year" is the period of a dog's (or other animal's) life that is claimed to be equivalent to a year of a human being's life (or seven calendar years).<ref>{{cite web
 | url         = http://www.dog-food-corner.com/dog-years-human-years-age.htm
 | title       = Dog-Food-Corner.com
 | archive-url = https://web.archive.org/web/20131214005631/http://www.dog-food-corner.com/dog-years-human-years-age.htm
 | archive-date= 14 December 2013}}</ref>

In fact, the aging of a dog varies by breed (larger breeds tend to have shorter lifespans than small and medium-sized breeds); dogs also develop faster and have longer adulthoods relative to their total life span than humans. Most dogs are sexually mature by 1&nbsp;year old, which corresponds to perhaps 13&nbsp;years old in humans. {{Citation needed|date=October 2023}} Giant dog breeds and bulldogs tend to have the strongest linear correspondence to human aging, with longer adolescences and shorter overall lifespans; such breeds typically age about nine times as fast as humans throughout their lives.<ref>{{cite web |url=http://www.pets911.com/hosted/buffalo/puppy/article.php?num=11045|archive-url=https://web.archive.org/web/20090610035254/http://www.pets911.com/hosted/buffalo/puppy/article.php?num=11045|archive-date=10 June 2009|title=Sexual Maturity&nbsp;— Spay and Neuter|publisher=Buffalo.com|access-date=22 October 2008}}</ref>

===Galactic year===
{{Main|Astronomy:Galactic year}}
The galactic year, GY, is the time it takes the solar system to revolve once around the galactic core, approximately 250&nbsp;million years ([[Megaannum|megaannum]] or "Ma"). It is a convenient unit for long-term measurements. For example, oceans appeared on Earth after 4&nbsp;GY, life is detectable at 5&nbsp;GY, and multicellular organisms first appeared at 15&nbsp;GY. The [[Earth:Age of the Earth|age of the Earth]] is estimated at 20&nbsp;GY.<ref>{{cite web |title=Geologic Time Galactic |url=http://www.vendian.org/mncharity/dir3/geologic_time_galactic/ |publisher=vendian.org |access-date=19 December 2006}}</ref> This use of GY is not to be confused with Gyr for gigayear or Gy for [[Physics:Gray (unit)|Gray (unit)]].

===KerMetric time===
KerMetric time is a concept that divides the day into 100 equal parts called kermits. Each kermit is equivalent to 14.4 minutes. More precise time can be counted by dividing by 1000 or even 10000. The name kermit came from a combination of the surname of Dr. Larkin Kerwin, president of the National Research Council in 1983, with the word "metric". The original working model of KerMetric time as conceived by W. Thayer of NRC was assembled by the designated Clock Construction Team of John Phillips, Ron Hawkins, Les Moore, and Willie Thayer in 1983.<ref>{{Cite web|url=http://www.csgnetwork.com/timemetricdispcalc3.html|title=KerMetric Time Display Calculator|website=www.csgnetwork.com}}</ref>

=== Moment ===
A [[Physics:Moment (unit)|moment]] was a [[History:Middle Ages|medieval]] unit of time. The movement of a shadow on a [[Engineering:Sundial|sundial]] covered 40&nbsp;moments in a [[Astronomy:Solar time|solar hour]]. An hour in this case meant one twelfth of the period between [[Astronomy:Sunrise|sunrise]] and [[Astronomy:Sunset|sunset]]. The length of a [[Astronomy:Solar time|solar hour]] depended on the length of the day, which in turn varied with the [[Physics:Season|season]], so the length of a moment in modern [[Second|second]]s was not fixed, but on [[Average|average]], a moment corresponded to 90 seconds.

===Thirds, fourths===

The term "[[Minute|minute]]" usually means {{frac|1|60}} of an [[Hour|hour]], coming from "a minute division of an hour". The term "[[Second|second]]" comes from "the [[Second#Sexagesimal divisions of calendar time and day|second minute division]] of an hour", as it is {{frac|1|60}} of a minute, or {{frac|1|60}} of {{frac|1|60}} of an hour. While usually sub-second units are represented with [[International System of Units|SI]] prefixes on the second (e.g. [[Millisecond|millisecond]]s), this system can be extrapolated further, such that a "Third" would mean {{frac|1|60}} of a second (16.7 milliseconds), and a "Fourth" would mean {{frac|1|60}} of a third (278 microseconds), etc. These units are occasionally used in astronomy to denote angles.<ref>{{Cite journal |last=Herschel |first=William |s2cid=186209747 |year=1785 |title=Catalogue of Double Stars |journal=[[Philosophy:Philosophical Transactions of the Royal Society|Philosophical Transactions of the Royal Society of London]] |volume=75 |pages=40–126 |jstor=106749 |doi=10.1098/rstl.1785.0006 }}</ref>

==Angular measure==

<!-- Please keep entries sorted in ascending order of magnitude, smallest first -->

=== Furman ===
The Furman is a unit of angular measure equal to {{frac|1|65,536}} of a circle, or just under 20&nbsp;[[Arcsecond|arcsecond]]s. It is named for Alan T. Furman, the American mathematician who adapted the [[CORDIC]] algorithm for 16-bit fixed-point arithmetic sometime around 1980.<ref>{{cite journal |last=Furman |first=Alan T. |title=The Cordic Algorithm for Fixed-Point Polar Geometry |url=http://www.forth.org/fd/FD-V04N1.pdf |journal=FORTH Dimensions |volume=4 |pages=14–15 |access-date=16 January 2009 }}</ref> 16&nbsp;bits give a resolution of 2<sup>16</sup> = 65,536 distinct angles.

===Binary degree, binary radian, brad===
A related unit of angular measure equal to {{Frac|1|256}} of a circle, represented by 8 bits, has found some use in machinery control where fine precision is not required, most notably crankshaft and camshaft position in [[Engine control unit|internal combustion engine controllers]], and in video game programming. There is no consensus as to its name, but it has been called the 8-Bit Furman, the Small Furman, the Furboy and more recently, the miFurman, (milli-binary-Furman). These units are convenient because they form cycles: for the 8-bit unit, the value overflows from 255 to 0 when a full circle has been traversed, so binary addition and subtraction work as expected. Measures are often made using a [[Gray code]], which is trivially converted into more conventional notation. Its value is equivalent to [[Physics:Turn (angle)#Tau proposals|Tau]]/256 radians, or about 0.0245436926&nbsp;radians.

===Grade ''(also grad, gradian, gon)''===
{{Main|Grad (angle)}}
Coordinates were measured in grades on official French terrestrial ordnance charts from the French revolution well into the 20th century. 1&nbsp;grade (or in modern symbology, 1&nbsp;gon) = 0.9° or 0.01 right angle. One advantage of this measure is that the distance between latitude lines 0.01&nbsp;gon apart at the equator is almost exactly 1&nbsp;kilometre ''(and would be exactly 1&nbsp;km if the original definition of 1&nbsp;metre = {{frac|1|10,000}} quarter-meridian had been adhered to)''. One disadvantage is that common angles like 30° and 60° are expressed by fractional values (33{{frac|1|3}} and 66{{frac|2|3}} respectively) so this "decimal" unit failed to displace the "sexagesimal" units equilateral-vertex – degree – minute – second invented by Babylonian astronomers.{{POV statement|date=October 2019}}

===Mils, strecks===
[[File:mil estimation.jpg|thumb|upright|Estimating mils by hand]]
''Mils'' and ''strecks'' are small units of angle used by various military organizations for range estimation and translating map coordinates used for directing artillery fire.<ref>{{cite book |title=Collins Concise Dictionary of the English Language|date=1982|isbn=978-0-00-433091-4|editor-first=William T|editor-last=Macleod}}</ref> The exact size varies between different organizations: there are 6400&nbsp;NATO mils per [[Physics:Turn (angle)|turn]] (1&nbsp;NATO mil&nbsp;= 0.982&nbsp;[[Milliradian|mrad]]), or 6000&nbsp;Warsaw pact mils per turn (1&nbsp;Warsaw pact mil&nbsp;= 1.047&nbsp;mrad). In the Swedish military, there are 6300&nbsp;strecks per turn (1&nbsp;streck&nbsp;= 0.997&nbsp;mrad).

===MERU (Milli Earth Rate Unit)===
The '''MERU''', or Milli Earth Rate Unit, is an angular velocity equal to 1/1000 of Earth's [[Astronomy:Sidereal time|rotation rate]]. It was introduced by MIT's Instrumentation Laboratories (now Draper Labs) to measure the performance of [[Earth:Inertial navigation system|inertial navigation system]]s.<ref>{{cite book|last=Brown|first=Russel H|title=Inertial Instrument System for Aerial Surveying|url=https://books.google.com/books?id=009p-dfd-kgC&pg=PA14|series=U.S. Geological Survey Professional Paper|volume=1390|year=1987|publisher=U.S. Government Printing Office|page=14}}</ref> One MERU = {{gaps|7.292|115| e=-8 | u=radians per second}}<ref name=IERS>{{cite web|url=http://hpiers.obspm.fr/eop-pc/models/constants.html|title=USEFUL CONSTANTS|website=Hpiers.obspm.fr|access-date=22 September 2018}}</ref> or about 0.2625&nbsp;milliradians/hour.

==Energy==

<!-- Please keep entries sorted in ascending order of magnitude, smallest first -->

===Gasoline gallon equivalent===
{{Main|Physics:Gasoline gallon equivalent}}
In 2011, the United States Environmental Protection Agency introduced the ''gallon gasoline equivalent'' as a unit of energy because their research showed most U.S. citizens do not understand the standard units. The gallon gasoline equivalent is defined as 33.7&nbsp;kWh,<ref name=EPAstudy10>{{cite web |url=http://www.epa.gov/fueleconomy/label/420r10909.pdf |archive-url=https://web.archive.org/web/20110213112025/http://www.epa.gov/fueleconomy/label/420r10909.pdf |archive-date=2011-02-13 |title=Environmental Protection Agency Fuel Economy Label – Final Report |website=US Environmental Protection Agency|date=September 2010|access-date=20 February 2011}}</ref> or about 1.213{{e|8}}&nbsp;joules.

Efficiency / fuel economy can be given as [[Physics:Miles per gallon gasoline equivalent|miles per gallon gasoline equivalent]].

===Tons of TNT equivalent===
The energy of various amounts of the explosive TNT (kiloton, megaton, gigaton) is often used as a unit of explosion energy, and sometimes of asteroid impacts and violent explosive volcanic eruptions. One ton of TNT produces 4.184{{e|9}}&nbsp;joules, or (by arbitrary definition) exactly {{10^|9}}&nbsp;[[Calorie|thermochemical calories]] (approximately 3.964{{e|6}}&nbsp;BTU). This definition is only loosely based on the actual physical properties of TNT.

===Hiroshima bomb and Halifax explosion===
[[File:Atomic cloud over Hiroshima - NARA 542192 - Edit.jpg|thumb|upright|Hiroshima bomb explosion]]
[[File:Halifax Explosion blast cloud.jpg|thumb|upright|Halifax explosion]]
The energy released by the Hiroshima bomb explosion (about 15&nbsp;kt TNT equivalent, or 6{{e|13}}&nbsp;J) is often used by [[Geologist|geologist]]s as a unit when describing the energy of [[Earth:Earthquake|earthquake]]s, volcanic eruptions, and [[Astronomy:Impact event|asteroid impact]]s.

Prior to the detonation of the Hiroshima bomb, the size of the Halifax Explosion (about 3&nbsp;kt TNT equivalent, or 1.26{{e|13}}&nbsp;J), was the standard for this type of relative measurement. Each explosion had been the largest known artificial detonation to date.<ref name=TimeDisaster>{{cite book |title=Time: Disasters that Shook the World|publisher=Time Home Entertainment|location=New York City|date=2012|page=56|isbn=978-1-60320-247-3}}</ref>

===Quad===
A [[Physics:Quad (unit)|quad]] is a unit of energy equal to {{10^|15}}&nbsp;[[British thermal unit|BTUs]], or approximately 1.055{{e|18}}&nbsp;J (slightly over one exajoule). It is suitably large to quantify energy usage by nations or by the planet as whole using everyday numbers. For example, in 2004, US energy consumption was about 100&nbsp;Q/year, while demand worldwide was about 400&nbsp;Q/year.<ref>{{cite journal |title=Basic Choices and Constraints on Long-Term Energy Supplies|date=July 2004 |journal=Physics Today|volume=57|issue=7|pages=47–52|doi=10.1063/1.1784302|last1=Weisz|first1=Paul B.|bibcode=2004PhT....57g..47W|doi-access=free}}</ref>

===Foe===
A [[Astronomy:Foe (unit)|foe]] is a unit of energy equal to {{10^|44}}&nbsp;[[Joule|joule]]s (≈9.478{{e|40}}&nbsp;[[British thermal unit|BTU]]) that was coined by physicist Gerry Brown of [[Organization:Stony Brook University|Stony Brook University]]. To measure the staggeringly immense amount of energy produced by a [[Astronomy:Supernova|supernova]], specialists occasionally use the "foe", an acronym derived from the phrase [ten to the power of] '''f'''ifty-'''o'''ne '''e'''rgs, or {{10^|51}}&nbsp;[[Physics:Erg|erg]]s. This unit of measure is convenient because a supernova typically releases about one foe of observable energy in a very short period of time (which can be measured in seconds).

==Other metric-compatible scales==
===Power: Ton of refrigeration===
{{Main|Ton of refrigeration}}
The rate at which heat is removed by melting {{convert|1|ST|kg|spell=in}} of ice in 24&nbsp;hours is called a ton of refrigeration, or even a ton of cooling. This unit of refrigeration capacity came from the days when large blocks of ice were used for cooling, and is still used to describe the heat-removal capabilities of refrigerators and chillers today. One ton of refrigeration is exactly equal to 12,000&nbsp;BTU/h, or 3.517&nbsp;kW.

===Luminous flux: watt equivalent===
With the phaseout of the incandescent lamp in the United States and European Union in the early 21st century, manufacturers and sellers of more energy-efficient lamps have compared the visible light output of their lamps to commonly used incandescent lamp sizes with the ''watt equivalent'' or ''watt incandescent replacement'' (usually with a lowercase w as a unit symbol, as opposed to capital W for the actual wattage). 1 watt incandescent replacement corresponds to 15 [[Lumen (unit)|lumens]]. Thus, a 72-watt [[Engineering:Halogen lamp|halogen lamp]], a 23-watt [[Physics:Compact fluorescent lamp|compact fluorescent lamp]] and a 14-watt [[Engineering:LED lamp|light-emitting diode lamp]], all of which emit 1500 lumens of visible light, are all marketed as "100 watt incandescent replacement" (100w).

===Flow: Amazon River===
The volume of discharge of the Amazon River sometimes used to describe large volumes of water flow such as ocean currents. The unit is equivalent to 216,000&nbsp;[[Cubic metre per second|m<sup>3</sup>/s]].<ref>{{cite web | title=Amazon River – Facts, History, Animals, & Map | website=Encyclopedia Britannica | url=https://www.britannica.com/place/Amazon-River | access-date=10 August 2019}}.</ref>

=== Flow: Sverdrup ===
One [[Sverdrup]] (Sv) is equal to 1,000,000 cubic metres per second (264,000,000&nbsp;USgal/s). It is used almost exclusively in [[Physics:Oceanography|oceanography]] to measure the volumetric rate of transport of [[Earth:Ocean current|ocean current]]s.

===Energy intensity===
The [[Langley (unit)|langley]] (symbol Ly) is used to measure solar radiation or insolation. It is equal to one thermochemical [[Calorie|calorie]] per square centimetre (4.184{{e|4}}&nbsp;J/m<sup>2</sup> or ≈3.684 BTU/sq&nbsp;ft) and was named after [[Biography:Samuel Pierpont Langley|Samuel Pierpont Langley]]. Its symbol should not be confused with that for the light-year, ly.

===Kinematic viscosity===
One of the few CGS units to see wider use, one [[Physics:Kinematic viscosity|stokes]] (symbol S or St) is a unit of [[Physics:Kinematics|kinematic]] [[Physics:Viscosity|viscosity]], defined as 1&nbsp;cm<sup>2</sup>/s, i.e., 10<sup>−4</sup>&nbsp;m<sup>2</sup>/s (≈1.08×10<sup>−3</sup>&nbsp;sq&nbsp;ft/s).

===Angular velocity===
'''MERU''' (Milli Earth Rate Unit), an [[Physics:Angular velocity|angular velocity]] equal to {{frac|1|1000}} of Earth's rotation rate: 1&nbsp;MERU = 0.015&nbsp;degrees/hour ≈ 0.072921 microradian/second. Sometimes used to measure the angular drift rate of an [[Earth:Inertial navigation system|inertial navigation system]].<ref>''Fundamentals of High Accuracy Inertial Navigation,'' Averil B. Chatfield, [American Institute of Aeronautics and Astronautics], 1997, p.32</ref>

===Electromagnetic flux===
In [[Astronomy:Radio astronomy|radio astronomy]], the unit of [[Physics:Flux|electromagnetic flux]] is the [[Astronomy:Jansky|jansky]] (symbol Jy), equivalent to 10<sup>−26</sup>&nbsp;[[Watt|watt]]s per square metre per [[Hertz|hertz]] (= 10<sup>−26</sup>&nbsp;kg/s<sup>2</sup> in base units, about 8.8×10<sup>−31</sup>&nbsp;BTU/ft<sup>2</sup>). It is named after the pioneering radio astronomer [[Biography:Karl Guthe Jansky|Karl Jansky]]. The brightest natural radio sources have flux densities of the order of one to one hundred jansky.

===Metre of water equivalent===
{{main|Physics:Meter water equivalent}}
A material-dependent unit used in [[Physics:Nuclear physics|nuclear]] and [[Physics:Particle physics|particle physics]] and engineering to measure the thickness of shielding, for example around a nuclear reactor, [[Physics:Particle accelerator|particle accelerator]], or [[Physics:Particle detector|radiation or particle detector]]. 1&nbsp;mwe of a material is the thickness of that material that provides the equivalent shielding of one metre (≈39.4&nbsp;in) of water.

This unit is commonly used in underground science to express the extent to which the overburden (usually rock) shields an underground space or laboratory from [[Astronomy:Cosmic ray|cosmic ray]]s. The actual thickness of overburden through which cosmic rays must traverse to reach the underground space varies as a function of direction due to the shape of the overburden, which may be a mountain, or a flat plain, or something more complex like a cliff side. To express the depth of an underground space in mwe (or kmwe for deep sites) as a single number, the convention is to use the depth beneath a flat overburden at [[Sea level|sea level]] that gives the same overall cosmic ray [[Physics:Muon|muon]] flux in the underground location.

===Strontium unit: radiation dose===
The [[Physics:Strontium unit|strontium unit]], formerly known as the Sunshine Unit (symbol S.U.), is a unit of biological contamination by radioactive substances (specifically [[Physics:Strontium-90|strontium-90]]). It is equal to one [[Physics:Curie (unit)|picocurie]] of Sr-90 per [[Gram|gram]] of body [[Chemistry:Calcium|calcium]]. Since about 2% of the human body mass is calcium, and Sr-90 has a [[Physics:Half-life|half-life]] of 28.78&nbsp;years, releasing 6.697+2.282&nbsp;[[Physics:Electronvolt|MeV]] per disintegration, this works out to about 1.065{{e|-12}}&nbsp;[[Physics:Gray (unit)|gray]]s per second. The permissible body burden was established at 1,000&nbsp;S.U.

===Banana equivalent dose===
[[File:Bananen Frucht.jpg|thumb|right|upright=.5|A banana contains [[Physics:Naturally occurring radioactive material|naturally occurring radioactive material]] in the form of potassium-40.]]
Bananas, like most organic material, naturally contain a certain amount of radioactive isotopes—even in the absence of any artificial pollution or contamination. The [[Physics:Banana equivalent dose|banana equivalent dose]], defined as the additional dose a person will absorb from eating one banana, expresses the severity of exposure to radiation, such as resulting from nuclear weapons or medical procedures, in terms that would make sense to most people. This is approximately 78&nbsp;nano[[Physics:Sievert|sievert]]s – in informal publications one often sees this estimate rounded up to 0.1&nbsp;μSv.

===Flight-time equivalent dose===
Natural background radiation typically increases with altitude above the earth's surface. Utilizing this phenomenon, dose resulting from radiological exposures can be expressed in units of flight-time. [[Physics:Flight-time equivalent dose|Flight-time equivalent dose]] is defined as the time spent in an aircraft at cruising altitude required to receive a radiological dose approximately equivalent to a radiological exposure such as a medical [[Physics:X-ray|x-ray]]. One hour of flight-time is approximately equivalent to a dose of 0.004&nbsp;milli[[Physics:Sievert|sievert]]s.

===Molar mass of cellulose===
In the pulp and paper industry, [[Physics:Molar mass|molar mass]] is traditionally measured with a method where the [[Physics:Intrinsic viscosity|intrinsic viscosity]] (dL/g) of the pulp sample is measured in cupriethylenediamine (Cuen). The intrinsic viscosity [η] is related to the weight-average molar mass (in daltons) by the Mark-Houwink equation: [η] = 0.070&nbsp;M<sub>w</sub><sup>0.70</sup>.<ref>{{Cite journal |doi = 10.1016/j.chroma.2013.01.038|pmid = 23398992|title = A re-investigation of the Mark–Houwink–Sakurada parameters for cellulose in Cuen: A study based on size-exclusion chromatography combined with multi-angle light scattering and viscometry|journal = Journal of Chromatography A|volume = 1281|pages = 32–37|year = 2013|last1 = Kes|first1 = Mürşide|last2 = Christensen|first2 = Bjørn E.}}</ref> However, it is typical to cite [η] values directly in dL/g, as the "viscosity" of the cellulose, confusingly as it is not a viscosity.

===Iodine, bromine and kappa number===
In measuring unsaturation in fatty acids, the traditional method is the [[Chemistry:Iodine value|iodine number]]. Iodine adds stoichiometrically to double bonds, so their amount is reported in grams of iodine spent per 100&nbsp;grams of oil. The standard unit is a dimensionless stoichiometry ratio of moles double bonds to moles fatty acid. A similar quantity, bromine number, is used in gasoline analysis.

In pulp and paper industry, a similar kappa number is used to measure how much bleaching a pulp requires. [[Chemistry:Potassium permanganate|Potassium permanganate]] is added to react with the unsaturated compounds (lignin and uronic acids) in the pulp and back-titrated. Originally with [[Chemistry:Bleaching of wood pulp#Chlorine and hypochlorite|chlorine bleaching]] the required quantity of [[Chemistry:Chlorine|chlorine]] could be then calculated, although modern methods use multiple stages. Since the oxidizable compounds are not exclusively lignin and the partially pulped lignin does not have a single stoichiometry, the relation between the kappa number and the precise [[Physics:Amount of substance|amount]] of lignin is inexact.

=== Temperature: Gas Mark ===
[[Physics:Gas Mark|Gas Mark]] is a temperature scale, predominantly found on British [[Engineering:Oven|oven]]s, that scales [[Earth:Linear scale|linearly]] with temperature above 135&nbsp;°C (Gas Mark 1) and scales with the [[Logarithmic scale|log]] of Celsius below 135&nbsp;°C.

==Demography and epidemiology==
[[Demography]] and quantitative [[Social:Epidemiology|epidemiology]] are statistical fields that deal with [[Count data|counts]] or proportions of people, or rates of change in these. [[Count data|Counts]] and proportions are technically [[Physics:Dimensionless quantity|dimensionless]], and so have no units of measurement, although identifiers such as "people", "births", "infections" and the like are used for clarity. Rates of change are [[Rate (mathematics)|counts per unit of time]] and strictly have inverse time dimensions (per unit of time). In [[Demography#Common rates and ratios|demography]] and epidemiology expressions such as [[Mortality rate|"deaths per year"]] are used to clarify what is being measured.

[[Prevalence]], a common measure in [[Social:Epidemiology|epidemiology]] is strictly a type of [[Medicine:Denominator data|denominator data]], a dimensionless ratio or proportion. [[Prevalence]] may be expressed as a fraction, a percentage or as the number of cases per 1,000, 10,000, or 100,000 in the population of interest.

===Micromort===
{{Main|Micromort}}
A micromort is a unit of [[Risk|risk]] measuring a one-in-a-million [[Probability|probability]] of [[Biology:Death|death]] (from [[Micro-|micro-]] and mortality). Micromorts can be used to measure riskiness of various day-to-day activities. A microprobability is a one-in-a million chance of some event; thus a micromort is the microprobability of death. For example, smoking 1.4&nbsp;cigarettes increases one's death risk by one micromort, as does traveling {{convert|230|mi|abbr=in|order=flip}} by car.

===Numbers of people: Stadium capacities===
[[File:AFL Grand Final 2010 on the Melbourne Cricket Ground.jpg|thumb|To make large numbers of people comprehensible, the capacity of large stadiums is often used. Here the Melbourne Cricket Ground (MCG) is in the process of filling with 100,016 spectators on AFL grand final day in 2010.]]
The large numbers of people involved in [[Demography|demography]] are often difficult to comprehend. A useful visualisation tool is the audience capacity of large sports stadiums (often about 100,000). Often the capacity of the largest stadium in a region serves as a unit for a large number of people. For example, Uruguay's Estadio Centenario is often used in Uruguay,<ref>{{cite web | title=Ahora la borrachera es "previa" a la fiesta | website=elpais.com.uy | date=15 October 2009 | url=http://www.elpais.com.uy/091011/pciuda-447246/ciudades/ahora-la-borrachera-es-previa-a-la-fiesta | archive-url=https://web.archive.org/web/20091015002051/http://www.elpais.com.uy/091011/pciuda-447246/ciudades/ahora-la-borrachera-es-previa-a-la-fiesta | archive-date=15 October 2009 | language=es | access-date=10 August 2019}}</ref><ref>{{cite web | title=The unemployed would fill three and a half Centennial Stadiums (Spanish) | website=LARED21 | date=7 November 2002 | url=http://www.lr21.com.uy/comunidad/97129-los-desocupados-colmarian-tres-y-medio-estadios-centenarios | language=es | access-date=10 August 2019}}</ref> while in parts of the United States, Michigan Stadium is used in this manner.{{Citation needed|date=February 2013}} In Australia, the capacity of the Melbourne Cricket Ground (about 100,000) is often cited in this manner. Hence the Melbourne Cricket Ground serves as both a measure of people and a unit of volume.<ref>{{cite web |author=Diabetes Australia|title=Diabetes – The Facts|url=https://www.diabetesaustralia.com.au/PageFiles/1615/the%20facts%20DA%20FINAL%202011.pdf|access-date=4 September 2014}}</ref><ref>{{cite web |author=NSW Department of Education and Communities|title=What the experts say about cyberbullying|url=http://www.schoolatoz.nsw.edu.au/technology/cyberbullying/what-the-experts-say |access-date=4 September 2014}}</ref><ref>{{cite web |author=The Age|title=Trouble brewing at the bottom of the bay|url=http://www.scubadoctor.com.au/article-bay-trouble-brewing.htm|access-date=4 September 2014}}</ref>

==Computer and information science==
The growth of computing has necessitated the creation of many new units, several of which are based on unusual foundations.

===Data volume===
[[File:Print vs. bytes.jpg|thumb|A CD-ROM can easily store the entirety of a paper encyclopedia's words and images, plus audio and video clips]]
Volume or capacity of data is often compared to works of literature or large collections of writing. Popular units include the Bible, the Encyclopædia Britannica, phone books, the complete works of Shakespeare, and the Library of Congress.

When the Compact Disc began to be used as a [[Engineering:Data storage device|data storage device]] as the [[CD-ROM]], journalists often described the disc capacity (650&nbsp;[[Megabyte|megabyte]]s) by using the number of Christian [[Religion:Bible|Bible]]s that can be stored. The King James Version of the Bible in uncompressed plain 8-bit text contains about 4.5&nbsp;million characters,<ref>{{cite book |url=http://www.gutenberg.org/ebooks/10|title=The Bible, Old and New Testaments, King James Version – Project Gutenberg|access-date=7 December 2011}}</ref> so a [[CD-ROM]] can store about 150&nbsp;[[Religion:Bible|Bible]]s.

The print version of the ''[[Encyclopædia Britannica]]'' is another common data volume metric. It contains approximately 300&nbsp;million characters,<ref>{{cite news |url=https://www.nytimes.com/1994/02/08/business/44-million-words-strong-britannica-to-join-internet.html?pagewanted=all&src=pm|author=John Markoff|title=44 Million Words Strong, Britannica to Join Internet|access-date=7 December 2011|date=8 February 1994|work=The New York Times}}</ref> so two copies would fit onto a [[CD-ROM]] and still have 50&nbsp;megabytes (or about 11&nbsp;bibles) left over.

The term ''Library of Congress'' is often used. It refers to the US Library of Congress. Information researchers have estimated that the entire print collections of the Library of Congress represent roughly 10&nbsp;[[Terabyte|terabyte]]s of uncompressed [[Text file|textual data]].<ref>{{cite web |url=http://www2.sims.berkeley.edu/research/projects/how-much-info/how-much-info.pdf#page=110|author=Peter Lyman|author2=Hal R. Varian|title=How Much Information?|access-date=29 November 2011|date=18 October 2000}}</ref>

====Nibble====
A measure of quantity of data or information, the "[[Nibble|nibble]]" (sometimes spelled "nybble" or "nybl") is normally equal to 4&nbsp;bits, or one half of the common 8-bit byte. The nibble is used to describe the amount of memory used to store a digit of a number stored in [[Binary-coded decimal|binary-coded decimal]] format, or to represent a single hexadecimal digit. Less commonly, 'nibble' may be used for any contiguous portion of a byte of specified length, e.g. "6-bit nibble"; this usage is most likely to be encountered in connection with a hardware architecture in which the word length is not a multiple of 8, such as older 36-bit minicomputers.

===FLOPS===
{{Main|FLOPS}}
In [[Computing|computing]], FLOPS (''FL''oating point ''O''perations ''P''er ''S''econd) is a measure of a computer's computing power. It is also common to see measurements of kilo, mega, giga, and teraFLOPS.

It is also used to compare the performance of computers in practice.<ref>{{cite web |title=TOP500 LIST November 2018 |url=https://top500.org/lists/2018/11/ |website=Top 500 |publisher=Top 500 |access-date=21 January 2019}}</ref>

=== BogoMips ===
{{Main|BogoMips}}
A measure to determine the [[Central processing unit|CPU]] speed. It was invented by Linus Torvalds and is nowadays present on every [[Software:Linux|Linux]] operating system. However, it is not a meaningful measure to assess the actual [[Central processing unit|CPU]] performance.

=== KLOC ===
A computer programming expression, the [[Source lines of code|K-LOC]] or KLOC, pronounced ''kay-lok'', standing for "kilo-[[Source lines of code|lines of code]]", i.e., thousand lines of code. The unit was used, especially by [[Company:IBM|IBM]] managers,<ref>{{cite web | title=Triumph of the Nerds: The Transcripts, Part II | website=PBS | url=https://www.pbs.org/nerds/part2.html | access-date=10 August 2019}}</ref> to express the amount of work required to develop a piece of software. Given that estimates of 20&nbsp;lines of functional code per day per programmer were often used, it is apparent that 1&nbsp;K-LOC could take one programmer as long as 50&nbsp;working days, or 10&nbsp;working weeks. This measure is no longer in widespread use because different computer languages require different numbers of lines to achieve the same result (occasionally the measure "assembly equivalent lines of code" is used, with appropriate conversion factors from the language actually used to assembly language).

Error rates in programming are also measured in "Errors per K-LOC", which is called the ''defect density''. NASA's [[Organization:Goddard Space Flight Center#Software Assurance Technology Center|SATC]] is one of the few organizations to claim zero defects in a large (>500K-LOC) project, for the space shuttle software.

An alternative measurement was defined by [[Software:Pegasus Mail|Pegasus Mail]] author David Harris: the "WaP" is equivalent to 71,500&nbsp;lines of program code, because that number of lines is the length of one edition of [[Biography:Leo Tolstoy|Leo Tolstoy]]'s ''War and Peace''.<ref>{{cite web | title=April 2017 – "How many WaPs is that?" | website=Pegasus Mail and Mercury | date=30 November 2011 | url=http://www.pmail.com/devnews_archive.htm | access-date=10 August 2019}}</ref>

===Ticks===
The "tick" is the amount of time between timer [[Interrupt|interrupt]]s generated by the timer circuit of a CPU. The amount of time is processor-dependent.<ref>{{cite book |last1=Laplante |first1=Phillip A. |last2=Ovaska |first2=Seppo J. |title=Real-Time Systems Design and Analysis: Tools for the Practitioner |date=22 November 2011 |publisher=John Wiley & Sons |isbn=978-0-470-76864-8 |page=122 |url=https://books.google.com/books?id=Ez6-aSfbqtsC&pg=PA122|language=en}}</ref><ref>{{cite book |last1=Bovet |first1=Daniel P. |last2=Cesati |first2=Marco |title=Understanding the Linux Kernel: From I/O Ports to Process Management |date=17 November 2005 |publisher=O'Reilly Media, Inc. |isbn=978-0-596-55491-0 |page=245 |url=https://books.google.com/books?id=h0lltXyJ8aIC&pg=PT245 |language=en}}</ref>

==Other==
{{anchor|Library of Congress}}

===Centipawn===
Chess software frequently uses centipawns internally or externally as a unit measuring how strong each player's situation position is, and hence also by how much one player is beating the other, and how strong a possible move is.<ref>{{cite web |url=http://chess-db.com/public/research/qualityofplay.html |title=Chess Play Quality Index |website=chess-db.com |access-date=1 May 2018 |archive-url=https://web.archive.org/web/20161211211029/http://chess-db.com/public/research/qualityofplay.html |archive-date=11 December 2016 }}</ref> 100&nbsp;centipawns = [[Chess piece relative value|the value of]] 1&nbsp;pawn – more specifically, something like the average value of the pawns at the start of the game, as the actual value of pawns depends on their position. Loss of a pawn will therefore typically lose that player 100&nbsp;centipawns. The centipawn is often used for comparing possible moves, as in a given position, chess software will often rate the better of two moves within a few centipawns of each other.

===Garn===
The garn is NASA's unit of measure for symptoms resulting from [[Astronomy:Space adaptation syndrome|space adaptation syndrome]], the response of the human body to weightlessness in space, named after US Senator Jake Garn, who became exceptionally spacesick during an orbital flight in 1985. If an astronaut is completely incapacitated by space adaptation syndrome, he or she is under the effect of one garn of symptoms.<ref>{{cite web | title=Robert E. Stevenson Oral History | website=NASA – Johnson Space Center History | date=13 May 1999 | url=https://historycollection.jsc.nasa.gov/JSCHistoryPortal/history/oral_histories/StevensonRE/StevensonRE_5-13-99.htm | access-date=10 August 2019}}</ref>

===Mother Cow Index===
Formerly used in real estate transactions in the American Southwest, it was the number of pregnant cows an acre of a given plot of land could support. It acted as a proxy for the agricultural quality, natural resource availability, and arability of a parcel of land.<ref>{{cite journal | title=Country Gentleman. v.75 1910. | journal=Better Farming1955 | date=2 January 2019 | hdl=2027/mdp.39015043511578 }}</ref>

===Nines===
{{Main|Nine (purity)}}
[[Image:Four nines fine gold.jpeg|thumb|upright|{{convert|1|ozt|g|lk=in}} of four nines fine gold (999,9)]]
Numbers very close to, but below one are often expressed in "nines" (N – not to be confused with the unit [[Newton (unit)|newton]]), that is in the number of nines following the decimal separator in writing the number in question. For example, "three nines" or "3N" indicates 0.999 or 99.9%, "four nines five" or "4N5" is the expression for the number 0.99995 or 99.995%.<ref>{{cite web |url=http://vikashazrati.wordpress.com/2008/10/24/truth-about-availabilit/|title=The Truth About Availability: What does 99.99% mean?|website=c0nnexx10n: C0nnect1ng L1fe w1th Techn010gy|date=24 October 2008}}</ref><ref>{{cite book|last1=McGachie|first1=Richard O. |last2=Bradley|first2=Anne Grace |title=Precious metals|url=https://books.google.com/books?id=KOMYAAAAIAAJ&pg=PA262|volume=4|year=1981|publisher=Pergamon|isbn=978-0-08-025369-5|page=262}}</ref><ref>{{cite book|title=PVD for Microelectronics: Sputter Desposition to Semiconductor Manufacturing|year=1998|page=[https://books.google.com/books?id=hmvtBE_7i00C&pg=PA387 387]}}<!-- NOTE: reference has typo, writing 99.9995% as "four-nines-five" while it is actually *five* nines five. --></ref>

Typical areas of usage are:
*The [[Reliability engineering|reliability]] of computer systems, that is the ratio of [[Uptime|uptime]] to the sum of [[Uptime|uptime]] and [[Downtime|downtime]]. "Five nines" reliability in a continuously operated system means an average [[Downtime|downtime]] of no more than approximately five minutes per year (there is no relationship between the number of nines and minutes per year, it is pure coincidence that "five nines" relates to five minutes per year.) (See [[High availability|high availability]] for a chart.)
*The [[Nine (purity)|purity]] of materials, such as gases and metals.

===Pain===
[[File:OuchFlintGoodrichShot1941.jpg|thumb|A woman wincing in pain]]
The dol (from the [[Social:Latin language|Latin]] word for pain, ''dolor'') is a [[Unit of measurement|unit of measurement]] for [[Medicine:Pain|pain]]. James D. Hardy, Herbert G. Wolff, and Helen Goodell of [[Organization:Cornell University|Cornell University]] proposed the unit based on their studies of pain during the 1940s and 1950s. They defined one dol to equal a [[Philosophy:Just-noticeable difference|just-noticeable difference]] in pain. The unit never came into widespread use and other methods are now used to assess the level of pain experienced by patients.

The Schmidt sting pain index and Starr sting pain index are pain scales rating the relative pain caused by different [[Biology:Hymenoptera|hymenoptera]] stings. Schmidt has refined his pain index (with a 1–4 scale) with extensive anecdotal experience, culminating in a paper published in 1990 which classifies the stings of 78&nbsp;species and 41 genera of [[Biology:Hymenoptera|Hymenoptera]]. The Starr sting pain scale uses the same 1–4 scale.

===Pepper heat===
====ASTA pungency unit====
The ASTA (American Spice Trade Association) pungency unit is based on a scientific method of measuring chili pepper "heat". The technique utilizes [[High-performance liquid chromatography|high-performance liquid chromatography]] to identify and measure the concentrations of the various compounds that produce a heat sensation. Scoville units are roughly {{frac|1|15}} the size of pungency units while measuring [[Chemistry:Capsaicin|capsaicin]], so a rough conversion is to multiply pungency by 15 to obtain Scoville heat units.<ref name="tainter">{{cite book |last= Tainter |first= Donna R.|author2=Anthony T. Grenis |date= 2001 |title= Spices and Seasonings |publisher= Wiley-IEEE |isbn= 978-0-471-35575-5 |url=https://books.google.com/books?id=dfp4b3F0598C&pg=PA30|page=30}} — "Interlab variation [for the original Scoville scale] could be as high as ±50%. However, labs that run these procedures could generate reasonably repeatable results."</ref>

====Scoville heat unit====
[[File:Madame Jeanette and other chillies.jpg|thumb|Chili peppers.]]
The [[Scoville scale]] is a measure of the hotness of a chili pepper. It is the degree of dilution in sugar water of a specific chili pepper extract when a panel of 5&nbsp;tasters can no longer detect its "heat".<ref name="what_is_scoville_scale">{{cite web |url=http://www.smithsonianmag.com/arts-culture/how-hot-is-that-pepper-how-scientists-measure-spiciness-884380/?no-ist |title=How Hot is That Pepper? How Scientists Measure Spiciness |website=www.smithsonianmag.com |access-date=20 June 2016}}</ref> Pure [[Chemistry:Capsaicin|capsaicin]] (the chemical responsible for the "heat") has 16&nbsp;million Scoville heat units.

===Potrzebie===
The widely-read MAD Magazine made extensive use, as a running gag, of the [[Potrzebie]] system of units, which included units of length, mass etc.

===Proof: alcohol concentration===
{{main|Alcohol proof}}
[[File:Bacardi 151 bottle.jpg|thumb|upright|A (nearly empty) bottle of 151° proof rum]]
Up to the 20th century, alcoholic spirits were assessed in the UK by mixing with gunpowder and testing the mixture to see whether it would still burn; spirit that just passed the test was said to be at 100°&nbsp;proof. The UK now uses percentage [[Chemistry:Alcohol by volume|alcohol by volume]] (ABV) at {{convert|20|C|1}}, where spirit at 100° proof is approximately 57.15%&nbsp;ABV. In the US, "proof number" is defined as twice the ABV at {{convert|60|F|1}}.<ref name=Jensen>{{cite journal|last=Jensen |first=William B. |date=September 2004 |title=The Origin of Alcohol 'Proof' |journal=Journal of Chemical Education |doi=10.1021/ed081p1258 |volume=81 |issue=9 |pages=1258–1259 |bibcode=2004JChEd..81.1258J |url=http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/111.%20Proof.pdf |access-date=17 July 2014 |archive-url=https://web.archive.org/web/20140708232531/http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/111.%20Proof.pdf |archive-date=8 July 2014}}</ref>

===Savart===
The [[Savart]] is an 18th-century unit for measuring the frequency ratio of two sounds. It is equal to {{frac|1|1000}} of a [[Decade (log scale)|decade]] (not to be confused with the time period equal to 10&nbsp;years). The [[Cent (music)|cent]] is preferred for musical use.

===Telecommunications traffic volume===
{{Main|Erlang (unit)}}
The erlang, named after A. K. Erlang, as a [[Physics:Dimensionless quantity|dimensionless unit]] is used in [[Engineering:Telephony|telephony]] as a statistical measure of the offered intensity of [[Engineering:Telecommunication|telecommunication]]s traffic on a group of resources. Traffic of one erlang refers to a single resource being in continuous use, or two channels being at fifty percent use, and so on, pro rata. Much telecommunications management and forecasting software uses this.

===X-ray intensity===
{{Main|Astronomy:Crab (unit)}}
The crab is defined as the intensity of X-rays emitted from the [[Astronomy:Crab Nebula|Crab Nebula]] at a given photon energy up to 30&nbsp;kiloelectronvolts. The Crab Nebula is often used for calibration of X-ray telescopes. For measuring the X-ray intensity of a less energetic source, the milliCrab (mCrab) may be used.

One crab is approximately 24&nbsp;pW/m<sup>2</sup>.

==See also==
{{Main|Outline of metrology and measurement}}
* [[Dimensional metrology]]
* [[Social:Forensic metrology|Forensic metrology]]
* [[Smart Metrology]]
* [[Time metrology]]
* [[Quantum metrology]]
{{div col|colwidth=30em}}
*[[Conversion of units]]
*[[Software:GNU Units|GNU Units]], a unit conversion program, which supports many uncommon units
*[[Hair's breadth]]
*[[History of measurement]]
*[[List of humorous units of measurement]]
*[[List of obsolete units of measurement]]
*[[Muggeseggele]]
*[[Unit of measurement]]
{{div col end}}

==References==
{{reflist}}

==Bibliography==
{{refbegin}}
*{{cite book |last=Berry|first=C. J. J. |title=First Steps in Winemaking|url=https://books.google.com/books?id=wz0CAQAACAAJ|year=1998|publisher=Nexus Special Interests|isbn=978-1-85486-139-9}}
*{{cite book |last=Regan|first=Gary |title=The Joy of Mixology|url=https://books.google.com/books?id=7TlhtrpXa-MC|year=2003|publisher=Clarkson Potter|isbn=978-0-609-60884-5}}
{{refend}}


{{DEFAULTSORT:List of Unusual Units of Measurement}}
[[Category:Lists of units of measurement|*]]
[[Category:Physics-related lists|Unusual units of measurement]]
[[Category:Units of measurement|Unusual units of measurement]]

{{Sourceattribution|List of unusual units of measurement}}