Inches and centimetres are both units of linear measurement. Inches are used in the American system, which is sometimes referred to as the English system. Centimetres are a unit of measurement in the metric system.

### American System

In the United States, the American system is the most commonly used method of measurement. This system uses inch, foot, yard and mile for measurements of length. The U.S. is the only industrialised nation that has not adopted the use of the metric system.

### Metric System

The meter is the basic unit on which the metric system is based. Because the metric system uses a standard conversion factor, it is usually considered easier to work with. Ten millimetres equal a centimetre, 10 centimetres equal a decimetre and 10 decimals equal a meter.

### Comparison

One inch equals 2.54 centimetres; one foot is 0.3048 meters; one yard is equal to 0.9144 meters and 1 mile equals 0.621 kilometres.

### Rulers

The standard U.S. ruler is divided into inches, with marks dividing each inch into sixteenths. Metric rulers are divided into centimetres, each with ten marks showing millimetres. Rulers showing both standard and metric measurements simplify conversion from inches to centimetres.

### Science

U.S. scientists commonly use the metric system, in order to standardise the measurements used in experiments around the world.