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The 'litre' or 'liter' (see spelling differences) is a unit of volume. There are two official symbols, namely the Latin letter L both in lower and upper case: 'l' and 'L'. The litre appears in several versions of the metric system; although not an SI unit, it is accepted for use with the SI. The international unit of volume is the cubic metre (m³). One litre is denoted as 1 dm³.

Contents

Origin

Definition

SI prefixes applied to the litre

Non-metric conversions

Rough conversions

Explanation

Symbol

History

Colloquial and practical usage

See also

References

External links

Origin

The word "litre" is derived from an older French unit, the ''litron'', whose name came from Greek via Latin. The original metric system used litre as a base unit.

Definition

A litre is defined as '' a special name for a cubic decimetre'' (1 L = 1 dm³). Hence 1 L ≡ 0.001 m³ (exactly).

SI prefixes applied to the litre

The litre may be used with any SI prefix. The more often used terms are in bold in the table below.

Multiple	Name	Symbols		Equivalent volume			Multiple	Name	Symbols		Equivalent volume
100 L	'litre'	l	L	dm³	cubic decimetre
101 L	decalitre	dal	daL	(10 dm³)			10–1 L	'decilitre'	dl	dL	(100 cm³)
102 L	'hectolitre'	hl	hL	(100 dm³)			10–2 L	'centilitre'	cl	cL	(10 cm³)
103 L	'kilolitre'	kl	kL	m³	'cubic metre'		10–3 L	'millilitre'	ml	mL	cm³	'cubic centimetre'
106 L	'megalitre'	Ml	ML	dam³	cubic decametre		10–6 L	microlitre	µl	µL	mm³	cubic millimetre
109 L	'gigalitre'	Gl	GL	hm³	cubic hectometre		10–9 L	nanolitre	nl	nL	106 µm³	1 million cubic micrometre
1012 L	teralitre	Tl	TL	km³	cubic kilometre		10–12 L	picolitre	pl	pL	103 µm³	1 thousand cubic micrometre
1015 L	petalitre	Pl	PL	103 km³	1 thousand cubic kilometre		10–15 L	femtolitre	fl	fL	µm³	cubic micrometre
1018 L	exalitre	El	EL	106 km³	1 million cubic kilometre		10–18 L	attolitre	al	aL	106 nm³	1 million cubic nanometre
1021 L	zettalitre	Zl	ZL	Mm³	cubic megametre		10–21 L	zeptolitre	zl	zL	103 nm³	1 thousand cubic nanometre
1024 L	yottalitre	Yl	YL	103 Mm³	1 thousand cubic megametre		10–24 L	yoctolitre	yl	yL	nm³	cubic nanometre

Non-metric conversions

Litre expressed in non-metric unit			Non-metric unit expressed in litre
1 L ≈ 0.87987699	Imperial quart		1 Imperial quart	≡ 1.1365225 litre
1 L ≈ 1.056688	US fluid quart		1 US fluid quart	≡ 0.946352946 litre
1 L ≈ 1.75975326	Imperial pint		1 Imperial pint	≡ 0.56826125 litre
1 L ≈ 2.11337641	US fluid pints		1 US fluid pint	≡ 0.473176473 litre
1 L ≈ 0.2641720523	US liquid gallon		1 US liquid gallon	≡ 3.785411784 litres
1 L ≈ 0.21997	Imperial gallon		1 Imperial gallon	≡ 4.54609 litres
1 L ≈ 0.0353146667	cubic foot		1 cubic foot	≡ 28.316846592 litres
1 L ≈ 61.0237441	cubic inches		1 cubic inch	≡ 0.01638706 litres
See also Imperial units and US customary units

Rough conversions

A litre is the volume of a cube with sides of 10 cm, which is slightly less than a cube of sides 4 inches (or one-third of a foot). Twenty-seven cubes "one-third of a foot on each side" would fit in one cubic foot, which is within 5% of the actual value of exactly 28.316846592 litres.
One litre is also slightly more than one U.S. liquid quart and slightly less than one Imperial quart or the less common U.S. dry quart.
A measured cup, is roughly 250 mL.

Explanation

Litres are most commonly used for items measured by the capacity or size of their container (such as fluids and berries), 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 (1 litre of chemically pure water has a mass of 1 kg at 277.13 K (3.98 °C or 39.164 °F), at which point the pure water occupies the minimum volume per mass). Similarly: 1 millilitre of water has about 1 g of mass; 1,000 litres of water has about 1,000 kg (1 tonne) of mass. This relationship is because the gram was originally defined as the mass of 1 mL of water. However, this definition was abandoned in 1964 because the density of water changes with pressure and the units of pressure are dependent on the definition of mass.

Symbol

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, 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. On some typewriters, particularly older ones, the unshifted L key had to be used to type the numeral 1. Further, even in some computer typefaces, the two characters are barely distinguishable at all. This caused some concern, especially in the medical community. As a result, 'L' (uppercase letter L) was accepted as an alternative symbol for litre in 1979. The United States National Institute of Standards and Technology now recommends the use of the uppercase letter L, 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, 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).
Prior to 1979, the symbol (script small l, U+2113), came into common use in some countries; for example, it was recommended by South African Bureau of Standards publication M33 in the 1970s. This symbol can still be encountered occasionally in some English-speaking countries, and its use is ubiquitous in Japan. Nevertheless, it is not used in most countries and not officially recognised by the BIPM, the International Organization for Standardization, or any national standards body.

History

In 1795, the litre was introduced in France as one of the new "Republican Measures", and defined as one cubic decimetre.
In 1879, the CIPM adopted the definition of the litre, and 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 1.000 028 dm³ (earlier reference works usually put it at 1.000 027 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. ^[1]
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.^[2]

Colloquial and practical usage

In spoken English, the abbreviation "mL" (for millilitre) is often pronounced as "mil", which is homophonous with the term "mil", meaning "one thousandth of an inch". This generally does not create confusion, because the context is usually sufficient — one being a volume, the other a linear measurement. The colloquial use of "mil" for milli'metre' for an ambiguous topic as in ''"5 mils of rain fell since 9am"'' may, however, be confusing.
The abbreviation 'cc' (for cubic centimetre) is also used colloquially for a millilitre, especially in the medical field, as well as in mechanics and related sports for combustion engine displacement.
In European countries where the metric system is common, the 'hectolitre' is the typical unit for production and export volumes of beverages (milk, beer, soft drinks, etc); 'decilitres' are found in cookbooks ; 'centilitres' indicate the capacity of drinking glasses and of small bottles. In colloquial Dutch in Belgium, a 'vijfentwintiger' and a 'drieëndertiger' (literally 'twenty-fiver' and 'thirty-threer') are the common beer glasses, the corresponding bottles mention 25 cL or 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 aka 0.5 L. Family size bottles as for soft drinks or drinking water use the 'litre' (0.5 L, 1 L, 1.5 L, 2 L), and so do beer barrels (50 L, or the half sized 25 L). This unit is most common for all other household size containers of liquids, from thermocans, by buckets, to bath tubs; as well as for fuel tanks and consumption for heating or by vehicles.
For larger volumes of fluids, such as annual consumption of tap water, lorry tanks, or swimming pools, the cubic metre is the general unit, as it is for all volumes of a non-liquid nature. There are a few exceptions in which the litre is used for rather large volumes, such as the irregularly shaped boot of a car or the internal size of a microwave oven.
In Canada, where SI is the official measuring system and in wide-spread use, consumer beverages are labelled almost exclusively using litres and millilitres. Hectolitres appear in industry, but centilitres and decilitres are rarely, if ever, used. Larger volumes are usually given in cubic metres (1 kL), or thousands or millions of cubic metres. The situation is similar in Australia, although 'kilolitres', 'megalitres' and 'gigalitres' are commonly used for measuring water consuption, reservoir capacities and river flows.

See also

★ Claude Émile Jean-Baptiste Litre

★ Pint

★ Gallon

★ Kilogram

★ Cubic metre

References

1. Appendix C: General tables of units of measurement
2. The International System of Units (SI), Bureau International des Poids et Mesures, , , , 2006,

External links

★ BIPM's "SI Brochure"

★ BIPM's "(Table 6 -) Non-SI units accepted for use with the International System"

★ NIST note on SI units

★ NIST recommends uppercase letter L

★ UK National physical laboratory's "Internationally recognised non SI units" page