Litre

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The litre or liter (U.S. spelling, see spelling differences) is a unit of volume. There are two official symbols, the Latin letter el in both cases: l and L. The litre is not an SI unit but is accepted for use with the SI. The SI unit of volume is the cubic metre (m³). It appears in several versions of the metric system.

Contents 1 Definition 2 SI prefixes applied to the litre 3 Name origin 4 Other common metric equivalencies 5 Conversions 5.1 Rough conversions 6 Explanation 7 Symbol 8 History 9 Colloquial usage 10 See also 11 References 12 External links

[edit] Definition

A litre is defined as a special name for a cubic decimetre (1 L = 1 dm³).

• 1 L = 0.001 m³ (exactly)

The original metric system used litres as a base unit.

[edit] SI prefixes applied to the litre

The litre may be used with any SI prefix. Unit names in bold indicate forms commonly heard in everyday's usage in various countries.

Multiple	Name	Symbols			Multiple	Name	Symbols
100	litre	l	L
101	decalitre	dal	daL		10–1	decilitre	dl	dL
102	hectolitre	hl	hL		10–2	centilitre	cl	cL
103	kilolitre	kl	kL		10–3	millilitre	ml	mL
106	megalitre	Ml	ML		10–6	microlitre	µl	µL
109	gigalitre	Gl	GL		10–9	nanolitre	nl	nL
1012	teralitre	Tl	TL		10–12	picolitre	pl	pL
1015	petalitre	Pl	PL		10–15	femtolitre	fl	fL
1018	exalitre	El	EL		10–18	attolitre	al	aL
1021	zettalitre	Zl	ZL		10–21	zeptolitre	zl	zL
1024	yottalitre	Yl	YL		10–24	yoctolitre	yl	yL

[edit] Name origin

The word "litre" is derived from an older French unit, the litron, whose name came from Greek via Latin.

[edit] Other common metric equivalencies

• 1 µL (microlitre) = 1 mm³ (cubic millimetre)
• 1 mL (millilitre) = 1 cm³ (cubic centimetre)

[edit] Conversions

One litre

≈ 0.87987699 Imperial quart

Inverse: One Imperial quart ≡ 1.1365225 litres

≈ 1.056688 US fluid quarts

Inverse: One US fluid quart ≡ 0.946352946 litres

≈ 1.75975326 Imperial pints

Inverse: One Imperial pint ≡ 0.56826125 litres

≈ 2.11337641 US fluid pints

Inverse: One US fluid pint ≡ 0.473176473 litres

≈ 0.2641720523 US liquid gallon

Inverse: One US liquid gallon ≡ 3.785411784 litres

≈ 0.21997 Imperial gallon

Inverse: One Imperial gallon ≡ 4.54609 litres

≈ 0.0353146667 cubic foot

Inverse: One cubic foot ≡ 28.316846592 litres

≈ 0.001 cubic meters (see definition)

Inverse: One cubic meter ≡ 1000 litres

[edit] 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 U.S. liquid quart and slightly less than one Imperial quart or the less common U.S. dry quart.

[edit] 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 (4 °C)). Similarly: 1 millilitre of water has about 1 g of mass; 1000 litres of water has about 1000 kg (1 tonne, or 1 megagram) 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.

[edit] 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 l key had to be used to type the numeral 1. Further, in some typefaces the two characters are nearly indistinguishable. 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 Britain 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 ℓ (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, but it is not used in most countries and not officially recognised by the BIPM, the International Organization for Standardization, or any national standards body.

[edit] History

In 1793, 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 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]

[edit] Colloquial usage

In spoken English, the abbreviation "mL" (for millilitre) is often pronounced as mil. The abbreviation cc (for cubic centimetre) is also used colloquially, especially in the medical field.

[edit] See also

• Claude Émile Jean-Baptiste Litre
• Pint
• Gallon
• Kilogram
• Cubic metre

[edit] References

1. ^ Appendix C: General tables of units of measurement. NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. National Institute of Standards and Technology (11 November 2000). Retrieved on 9 October 2006.
2. ^ Bureau International des Poids et Mesures (2006). The International System of Units (SI), 159.

[edit] 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