The metric system is the most common system of measures. Units of measure are fixed.

Length is measured in metres (m).

A metre is the same as 100 centimetres (cm). 'Centi-' means one hundredth.

A metre is the same as 1000 millimetres (mm). 'Milli-' means one thousandth.

Material is sold by the metre. Clothes are labelled in centimetres.