The litre or liter (see spelling ifferences) is a unit of volume. There are two official symbols: the Latin letter L in lower (l) and upper case (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 equal to 0.001 cubic metre and is denoted as 1 cubic decimetre (dm3).