Litre#History

{{visualisation_litre_gram.svg}}

A litre is a cubic decimetre, which is the volume of a cube 10 centimetres × 10 centimetres × 10 centimetres (1 L ≡ 1 dm³ ≡ 1000 cm³). Hence 1 L ≡ 0.001 m³ ≡ 1000 cm³; and 1 m³ (i.e. a cubic metre, which is the SI unit for volume) is exactly 1000 L.

From 1901 to 1964, the litre was defined as the volume of one kilogram of pure water at maximum density (+3.98 °C){{citation needed|date=September 2023}} and standard pressure. The kilogram was in turn specified as the mass of the International Prototype of the Kilogram (a specific platinum/iridium cylinder) and was intended to be of the same mass as the 1 litre of water referred to above. It was subsequently discovered that the cylinder was around 28 parts per million too large and thus, during this time, a litre was about {{val|1.000028|u=dm3}}. Additionally, the mass–volume relationship of water (as with any fluid) depends on temperature, pressure, purity and isotopic uniformity. In 1964, the definition relating the litre to mass was superseded by the current one. Although the litre is not an SI unit, it is accepted by the CGPM (the standards body that defines the SI) for use with the SI. CGPM defines the litre and its acceptable symbols.

A litre is equal in volume to the millistere, an obsolete non-SI metric unit formerly customarily used for dry measure.

Litres are most commonly used for items (such as fluids and solids that can be poured) which are measured by the capacity or size of their container, whereas cubic metres (and derived units) are most commonly used for items measured either by their dimensions or their displacements. The litre is often also used in some calculated measurements, such as density (kg/L), allowing an easy comparison with the density of water.

One litre of water has a mass of almost exactly one kilogram when measured at its maximal density, which occurs at 3.984 °C. It follows, therefore, that {{sfrac|1000}} of a litre, known as one millilitre (1 mL), of water has a mass of about 1 g, while 1000 litres of water has a mass of about 1000 kg (1 tonne or megagram).

This relationship holds because the gram was originally defined as the mass of 1 mL of water; however, this definition was abandoned in 1799 because the density of water changes with temperature and, very slightly, with pressure.

It is now known that the density of water also depends on the isotopic ratios of the oxygen and hydrogen atoms in a particular sample. Modern measurements of Vienna Standard Mean Ocean Water, which is pure distilled water with an isotopic composition representative of the average of the world's oceans, show that it has a density of {{val|0.999975|0.000001|u=kg/L}} at its point of maximum density (3.984 °C) under one standard atmosphere (101.325 kPa) of pressure.Isotopic composition and temperature per London South Bank University's [http://www1.lsbu.ac.uk/water/data.html "List of physicochemical data concerning water"], density and uncertainty per [http://webbook.nist.gov/chemistry/ NIST Standard Reference Database Number 69] (Retrieved: 2010-04-05).

The litre, though not an official SI unit, may be used with SI prefixes. The most commonly used derived unit is the millilitre, defined as one-thousandth of a litre, and also often referred to by the SI derived unit name "cubic centimetre". It is a commonly used measure, especially in medicine, cooking and automotive engineering. Other units may be found in the table below, where the more often used terms are in bold. However, some authorities advise against some of them; for example, in the United States, NIST advocates using the millilitre or litre instead of the centilitre.Kenneth Butcher, Linda Crown, Elizabeth J. Gentry (2006), [http://ts.nist.gov/WeightsAndMeasures/Metric/upload/SP1038.pdf The International System of Units (SI) – Conversion Factors for General Use]. {{webarchive|url=https://web.archive.org/web/20100527160710/http://ts.nist.gov/WeightsAndMeasures/Metric/upload/SP1038.pdf |date=27 May 2010 }}, NIST Special Publication 1038. There are two international standard symbols for the litre: L and l. In the United States the former is preferred because of the risk that (in some fonts) the letter {{code|l}} and the digit {{code|1}} may be confused.{{cite journal |url=https://www.nist.gov/pml/special-publication-811/nist-guide-si-chapter-5-units-outside-si#table6 |title= Table 6. Non-SI units accepted for use with the SI by the CIPM and this Guide | publisher= National Institute of Standards and Technology | author1= A. Thompson | author2= B. N. Taylor |journal= NIST | orig-year= First published 2 July 2009 | date = 4 March 2020 | access-date= 30 March 2020}} See footnote (b).

See also Imperial units and US customary units.

One litre is about {{val|5.7|u=%}} larger than a US liquid quart, and about {{val|12|u=%}} smaller than an imperial quart.

A mnemonic for its volume relative to an imperial pint is "a litre of water's a pint and three-quarters"; this is very close, as a litre is about 1.760 imperial pints.

A cubic foot has a volume of exactly {{val|28.316846592|u=litres}}.

Originally, the only symbol for the litre was l (lowercase letter L), following the SI convention that only those unit symbols that abbreviate the name of a person start with a capital letter. In many English-speaking countries, however, the most common shape of a handwritten Arabic digit 1 is just a vertical stroke; that is, it lacks the upstroke added in many other cultures. Therefore, the digit "1" may easily be confused with the letter "l". In some computer typefaces, the two characters are barely distinguishable. As a result, L (uppercase letter L) was adopted by the CIPM as an alternative symbol for litre in 1979.{{cite web |url=https://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf |title=The International System of Units (SI) |date=2006 |page=124 |access-date=20 February 2021 |archive-date=14 August 2017 |archive-url=https://web.archive.org/web/20170814094625/http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf |url-status=dead }} The United States National Institute of Standards and Technology now recommends the use of the uppercase letter L,[http://physics.nist.gov/Pubs/SP811/sec05.html#table6 Non-SI units accepted for use with the SI by the CIPM] – NIST. a practice that is also widely followed in Canada and Australia. In these countries, the symbol L is also used with prefixes, as in mL and μL, instead of the traditional ml and μl used in Europe. In the UK and Ireland, as well as the rest of Europe, lowercase l is used with prefixes, though whole litres are often written in full (so, "750 ml" on a wine bottle, but often "1 litre" on a juice carton). In 1990, the International Committee for Weights and Measures stated that it was too early to choose a single symbol for the litre.

Prior to 1979, the symbol {{Litre}} came into common use in some countries;{{citation needed|date=September 2019}} for example, it was recommended by South African Bureau of Standards publication M33 and Canada in the 1970s. This symbol can still be encountered occasionally in some English-speaking and European countries, and its use is ubiquitous in Japan and South Korea.{{fact|date=February 2025}}

Fonts covering the CJK characters usually include not only the script small {{Litre}} but also four precomposed characters: {{not a typo|㎕, ㎖, ㎗, and ㎘}} for the microlitre, millilitre, decilitre and kilolitre to allow correct rendering for vertically written scripts. These have Unicode equivalents for compatibility, which are not recommended for use with new documents:{{cite web |url=https://www.unicode.org/charts/PDF/U3300.pdf |access-date=24 May 2019 |title=The Unicode Standard 12.0 – CJK Compatibility ❰ Range: 3300—33FF ❱ |author=Unicode Consortium |author-link=Unicode Consortium |date=2019 |website=Unicode.org}}

• {{unichar|2113|Script Small L}}
• {{unichar|3395|Square MU L}}
• {{unichar|3396|Square ML}}
• {{unichar|3397|Square DL}}
• {{unichar|3398|Square KL}}

The CJK Compatibility block also includes {{unichar|3351}} corresponding to {{lang|ja|リットル}} {{transl|ja|rittoru}}, Japanese for 'litre'.

The first name of the litre was "cadil"; standards are shown at the Musée des Arts et Métiers in Paris.{{cite web

|url = http://2007.artsetmetiers.net/pdf/DEFPC_VG_COLLEGE.pdf

|archive-url = https://web.archive.org/web/20131109202133/http://2007.artsetmetiers.net/pdf/DEFPC_VG_COLLEGE.pdf

|url-status = dead

|archive-date = 9 November 2013

|title = Visite Générale au Musée des arts et métiers

|publisher = Musée des arts et métiers

|location = Paris

|quote = Comment s'est appelé cet étalon de mesure avant de s'appeler le litre ? - Le Cadil [What was the name of this measurement before called being called a litre? - a Cadil].

|access-date = 5 August 2013

}}

The litre was introduced in France in 1795 as one of the new "republican units of measurement" and defined as one cubic decimetre.{{cite web

|url = http://www.metrodiff.org/cmsms/index.php?page=18_germinal_an_3

|title = Décret relatif aux poids et aux mesures du 18 germinal an 3 (7 avril 1795)

|language = fr

|trans-title = Weights and measures decree dated 18 Germinal, Year 3 (7 April 1795)

|publisher = Association Métrodiff

|date = 7 April 1795

|quote = Litre, la mesure de capacité, tant pour les liquides que pour les matières sèches, dont la contenance sera celle du cube de la dixièrne partie du mètre.

|access-date = 8 December 2012

|archive-url = https://web.archive.org/web/20160817122340/http://www.metrodiff.org/cmsms/index.php?page=18_germinal_an_3

|archive-date = 17 August 2016

|url-status = dead

}} English translation: "Litre: unit of capacity for both liquids and solids which will be equivalent to a cube of [with sides] one tenth of a metre."

One litre of liquid water has a mass of almost exactly one kilogram, due to the gram being defined in 1795 as one cubic centimetre of water at the temperature of melting ice.{{cite web |date=7 April 1795 |title=Décret relatif aux poids et aux mesures du 18 germinal an 3 (7 avril 1795) |trans-title=Weights and measures decree dated 18 Germinal, Year 3 (7 April 1795) |url=http://www.metrodiff.org/cmsms/index.php?page=18_germinal_an_3 |url-status=dead |archive-url=https://web.archive.org/web/20160817122340/http://www.metrodiff.org/cmsms/index.php?page=18_germinal_an_3 |archive-date=17 August 2016 |access-date=8 December 2012 |publisher=Association Métrodiff |language=fr |quote=Gramme, le poids absolu d'un volume d'eau pure égal au cube de la centième partie du mètre, et à la température de la glace fondante.}} English translation: "Gramme: the absolute weight of a volume of pure water equal to the cube of the hundredth part of the metre, at the temperature of melting ice."

The original decimetre length was 44.344 lignes, which was revised in 1798 to 44.3296 lignes. This made the original litre {{val|1.000974}} of today's cubic decimetre. It was against this litre that the kilogram was constructed.

In 1879, the CIPM adopted the definition of the litre, with the symbol l (lowercase letter L).

In 1901, at the 3rd CGPM conference, the litre was redefined as the space occupied by 1 kg of pure water at the temperature of its maximum density (3.98 °C) under a pressure of 1 atm. This made the litre equal to about {{val|1.000028|u=dm3}} (earlier reference works usually put it at {{val|1.000027|u=dm3}}).

In 1964, at the 12th CGPM conference, the original definition was reverted to, and thus the litre was once again defined in exact relation to the metre, as another name for the cubic decimetre, that is, exactly 1 dm³.{{cite web|url=http://ts.nist.gov/WeightsAndMeasures/Publications/appxc.cfm#4e |title=NIST, 2000 |publisher=Ts.nist.gov |access-date=2012-04-26 |url-status=dead |archive-url=https://web.archive.org/web/20111210164956/http://ts.nist.gov/weightsandmeasures/publications/appxc.cfm |archive-date=10 December 2011 }}

In 1979, at the 16th CGPM conference, the alternative symbol L (uppercase letter L) was adopted. It also expressed a preference that in the future only one of these two symbols should be retained, but in 1990 said it was still too early to do so.{{cite web|url=http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf |title=Bureau International des Poids et Mesures, 2006 |access-date=2012-04-26}}

In spoken English, the symbol "mL" (for millilitre) can be pronounced as "mil". This can potentially cause confusion with some other measurement words such as:

1. "mm" for millimetre, a unit of length equal to one-thousandth of a metre
2. "mil" for thousandth of an inch
3. "mil", a Scandinavian unit of length equal to 10 kilometres
4. "mil", unit of angular measurement

The abbreviation "cc" (for cubic centimetre, equal to a millilitre or mL) is a unit of the cgs system, which preceded the MKS system, which later evolved into the SI system. The abbreviation "cc" is still commonly used in many fields, including medical dosage and sizing for combustion engine displacement.

The microlitre (μL) has been known in the past as the lambda (λ), but this usage is now discouraged.{{cite book |first1=Carl A. |last1=Burtis |first2=David E. |last2=Bruns |year=2014 |title=Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics |edition=7. |publisher=Elsevier Health Sciences |isbn=9780323292061 |url=https://books.google.com/books?id=p7XwAwAAQBAJ&pg=PA114 |pages=114}} In the medical field the microlitre is sometimes abbreviated as mcL on test results.{{cite web |title=Units of Measurement |url=http://www.mayomedicallaboratories.com/test-catalog/appendix/measurement.html |website=Mayo Medical Laboratories |access-date=23 June 2017 |language=en}}

File:Two shot glasses.jpges with centilitre fill line graduations. "ARC" is the maker's (Arc International) certification of accuracy.]]

In the SI system, apart from prefixes for powers of 1000, use of the "centi" (10⁻²), "deci" (10⁻¹), "deca" (10⁺¹) and "hecto" (10⁺²) prefixes with litres is common. For example, in many European countries, the hectolitre is the typical unit for production and export volumes of beverages (milk, beer, soft drinks, wine, etc.) and for measuring the size of the catch and quotas for fishing boats; decilitres are common in Croatia, Switzerland and Scandinavia and often found in cookbooks, and restaurant and café menus; centilitres indicate the capacity of drinking glasses and of small bottles. In colloquial Dutch in Belgium, a "{{lang|nl|vijfentwintiger}}" and a "{{lang|nl|drieëndertiger}}" (literally "twenty-fiver" and "thirty-threer") are the common beer glasses, the corresponding bottles mention 25 cL and 33 cL. Bottles may also be 75 cL or half size at 37.5 cL for "artisanal" brews or 70 cL for wines or spirits. Cans come in 25 cL, 33 cL and 50 cL.{{citation needed|date=October 2019}} Similarly, alcohol shots are often marked in cL in restaurant menus, typically {{cvt|3|cL|floz|2}}.

File:Gasoline unit.svg units used in the world:

{{legend|#ff0000|Litre}}{{legend|#00ff00|US gallon}}{{legend|#0000ff|Imperial gallon}}{{legend|#e0e0e0|No data}}]]

In countries where the metric system was adopted as the official measuring system after the SI standard was established, common usage eschews prefixes that are not powers of 1000. For example, in Canada, Australia, and New Zealand, consumer beverages are labelled almost exclusively using litres and millilitres. An exception is in pathology, where for instance blood lead level{{cite web|url=http://lead-info.com/levelschart.html |title=Blood Lead Levels Chart |access-date=21 November 2021}} and blood sugar level{{cite web|url=https://diabetesmealplans.com/wp-content/uploads/2016/05/DMP-BloodSugar-Levels-Chart.pdf |title=Diabetes Blood Sugar Level Chart |access-date=21 November 2021}} may be measured in micrograms/milligrams per decilitre.

For larger volumes, kilolitres, megalitres, and gigalitres, have been used by the Northern Territory Government for measuring water consumption, reservoir capacities and river flows,[https://depws.nt.gov.au/__data/assets/pdf_file/0004/589477/waterres-nt-factsheet-watervolumes.pdf Water volumes - how much water?], Northern Territory Government although cubic metres are also used. Cubic metres are generally used for non-liquid commodities, such as sand and gravel, or storage space.

• {{annotated link|Claude Émile Jean-Baptiste Litre}}
• Unit of volume

{{Notelist}}

{{Reflist}}

• {{cite web |author=Bureau International des Poids et Mesures |title=The International System of Units (SI) |year=2006 |url= http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf | access-date=2008-08-18}}
• Bureau International des Poids et Mesures. (2006). [http://www.bipm.org/en/si/si_brochure/ "The International System of Units (SI)"] (on-line browser):
• [https://web.archive.org/web/20091001100650/http://www.bipm.org/en/si/si_brochure/chapter4/table6.html Table 6] (Non-SI units accepted for use with the International System). Retrieved 2008-08-24
• {{cite web|author=National Institute of Standards and Technology |title=Appendix C: General tables of units of measurement |work=NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices |publisher=National Institute of Standards and Technology |date=11 November 2000 |url=http://ts.nist.gov/WeightsAndMeasures/Publications/appxc.cfm#4e |access-date=2006-10-09 |url-status=dead |archive-url=https://web.archive.org/web/20111210164956/http://ts.nist.gov/weightsandmeasures/publications/appxc.cfm |archive-date=10 December 2011 }}
• National Institute of Standards and Technology. (December 2003). [https://web.archive.org/web/20041111030930/http://physics.nist.gov/cuu/Units/index.html The NIST Reference on Constants, Units, and Uncertainty: International System of Units (SI)] (web site):
• [http://physics.nist.gov/cuu/Units/units.html Note on SI units]. Retrieved 2008-08-24.
• [http://physics.nist.gov/cuu/Units/outside.html Recommending uppercase letter L]. Retrieved 2008-08-24.
• Taylor, B.N. and Thompson, A. (Eds.). (2008a). [http://physics.nist.gov/Pubs/SP330/sp330.pdf The International System of Units (SI)] {{Webarchive|url=https://web.archive.org/web/20160603215953/http://physics.nist.gov/Pubs/SP330/sp330.pdf |date=3 June 2016 }}. United States version of the English text of the eighth edition (2006) of the International Bureau of Weights and Measures publication Le Système International d' Unités (SI) (Special Publication 330). Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 2008-08-18.
• Taylor, B.N. and Thompson, A. (2008b). [http://physics.nist.gov/cuu/pdf/sp811.pdf Guide for the Use of the International System of Units] (Special Publication 811). Gaithersburg, MD: National Institute of Standards and Technology. Retrieved 2008-08-23.
• Turner, J. (Deputy Director of the National Institute of Standards and Technology). (16 May 2008).[https://web.archive.org/web/20090326162948/http://ts.nist.gov/WeightsAndMeasures/Metric/upload/FRN_Vol_73_No_96_16May2008_SI_Interpretation.pdf "Interpretation of the International System of Units (the Metric System of Measurement) for the United States"]. Federal Register Vol. 73, No. 96, p. 28432-3.
• UK National Physical Laboratory. [http://www.npl.co.uk/reference/measurement-units/non-si-units/ Non-SI Units]

{{SI units}}

Category:Alcohol measurement

Category:Non-SI metric units

Category:Units of volume

Category:Cooking weights and measures