In the metric system, there is a unit fixed to each of these measurements: metre in length, gramme in weight, and litre in capacity. The metre is the primary basis of this measurement, which in length is equal to 39.370432 inches.

' Liquid measure is obtained by making the unit or standard a litre, equal in capacity to a cubic decimetre, equal to 0.2617 English gallon; dry measure, by making the standard a hectolitre, equal to 2 bushels and 3.35 pecks; while for solid the standard is a stere, equal to a cubic metre, equal to 35.317 cubic feet English. Lastly, to complete the series, weight is allied to the metre, by making the kilogramme to correspond with the contents of a cubic vessel of distilled water at the temperature of 40 C, or slightly above melting ice, the side of which is the tenth part of a metre (the decimetre), and the gramme to answer to the contents of a cubic vessel, the side of which is the hundredth part of the metre (the centimetre); for the contents of all cubic vessels are to each other in a triplicate ratio of their sides. (Euclid, 33. xi) All hese units, by the prefixes, deca., deci, hecto, milli, etc., become applicable to any weight and measure, and as the multiple of 10 connects all the larger and smaller measures, the whole becomes susceptible of decimal computation." - Dunglison's Reference Book.

In order to express the decimal proportions, the following prefixes are used.