Definition

The litre is no longer one of the standard units of the metric system (SI), although it was a base unit in many incarnations of the metric system. It is now defined in terms of the SI unit of length, as volume is a three dimensional measure, and is considered a special name for 1 cubic decimetre (see below)

• 1 decimetre = 0.1 metres = 10 centimetres

Thus 1 cubic metre, the SI metric unit of volume is 1000 litres and 1 litre is 1000 cubic centimetres.

Usage

The litre and its derivative measures (centilitres, millilitres etc) are commonly used for measuring the volumes of liquids and items that are measured by the size of their container. You will find that in almost all European countries and other countries that have adopted the metric system that milk, beer, water and other drinks will be sold in containers measured in litres, centilitres or millilitres. Some countries such as the UK use the millilitre much more than the centilitre and others use the centilitre in preference to the millilitre.

Table of Metric Liquid Volume Units

The following table gives metric liquid volume units, the litre and its derivatives (using standard SI metric prefixes), with their equivalent in both UK pints and US pints.

Unit	Abbreviation	As Litres	As UK Pints	As US Pints	Notes
microlitre	μl	0.000001	0.00000175975399	0.000002113376419	Used on pharmaceutical packaging
millilitre	ml	0.001	0.00175975399	0.002113376419	Used on food and pharmaceutical labels and packages
centilitre	cl	0.01	0.0175975399	0.02113376419	Used on drinks containers in mainland Europe
decilitre	dl	0.1	0.175975399	0.2113376419	Rarely used
litre	l	1	1.75975399	2.113376419	litres are commonly used in retail sales
decalitre	dal	10	17.5975399	21.13376419	Rarely used
hectolitre	hl	100	175.975399	211.3376419	Rarely used
kilolitre	kl	1,000	1,759.75399	2,113.376419
megalitre	Ml	1,000,000	1,759,753.99	2,113,376.419

History & Background

The litre was one of the original metric base units introduced in the French metric system of 1799. It was part of the official metric system until 1964, when the current definition was introduced. For many years before this it was defined as the volume of 1 kilogram of pure water at maximum density and standard atmospheric pressure.

Conversion Formulae for Litres

To British Imperial - Pints

• 1 litre = 1.75975399 Imperial pints
• 1 Imperial pint = 0.56826125 litres

To US Customary - Pints

• 1 litre = 2.113376419 US pints
• 1 US pint = 0.473176473 litres