A centimeter (cm), or centimetre, is a unit of length in the metric system of measurement. It is a fraction of the meter (m), the base unit of length in the International System of Units (SI).

The prefix "centi-" indicates that a centimeter is meters. There are a number of other metric prefixes.

Originally, the centimeter was its own base unit in the centimetre-gram-second (CGS) system of units, but this system is not really used anymore.

Centimeters and other units of length

The centimeter is one of the most common and practical units of length used around the world. Below are a few others, along with their relationship to the centimeter.

2.54 centimeters = 1 inch

1 centimeter = 10 millimeters

100 centimeters = 1 meter

Rulers are a measurement device that you may come across in everyday life. They often have measurements with centimeters (and millimeters) on one side, and inches on the other, like in the figure below.

If your child has misplaced your ruler and you just need to estimate a length, note that a the width of a child's pinky finger is roughly 1 centimeter!