Centimetre

The centimetre (symbol: cm) is a unit of length in the metric system. One centimetre equals one hundredth of a metre, meaning each metre contains 100 centimetres. The name comprises the prefix 'centi-', meaning one hundredth, and the word 'metre'.

The centimetre is one of the units of length most commonly used in everyday life, particularly for measuring human height, clothing sizes, pictures, and small objects. When measuring long distances, metres and kilometres are used; when measuring very small objects, millimetres are preferred.

Relationship to other units

One centimetre equals 10 millimetres and 0.01 metres. One thousand centimetres equals 10 metres. In conversion to the imperial system, one inch (in) equals exactly 2.54 centimetres, so one centimetre is approximately 0.394 inches.

Status in the SI system

The International System of Units (SI) designates the metre as the base unit of length, with the centimetre derived from it using a prefix. Formerly, in the CGS system (centimetre–gram–second), the centimetre was the base unit of length; that system is no longer in formal use, though some of its units persist in physics research.

Derived units

The centimetre has derived units in two and three dimensions: the square centimetre (cm²), used for measuring area, and the cubic centimetre (cm³), used for measuring volume. One cubic centimetre equals one millilitre, making it a standard measure for medical syringes and pipettes.