Length Converter

How length units fit together

Every length unit on this site is defined against the meter. Metric units are the meter moved by a power of ten: a millimeter is a thousandth, a centimeter a hundredth, a kilometer a thousand meters. The US and imperial units have been fixed to the meter since 1959, when the inch was set at exactly 25.4 millimeters. Everything else follows from that: a foot is 12 inches (0.3048 m), a yard is 3 feet (0.9144 m) and a mile is 5,280 feet (1,609.344 m).

Because those definitions are exact, converting inches, feet, yards or miles to metric never needs a rounded factor. Going the other way does: 1 centimeter is 1 ÷ 2.54 inches, a decimal that never ends. The converters here keep that value as an exact fraction and round only the number you see, so a result is as precise as the decimals you ask for.

A decimal inch is not much use on a tape measure. Pick inches or feet as the result unit and switch on inch fractions to round to the nearest 1/16, 1/32 or 1/64. The converter also tells you how far that mark is from the exact value. Feet are shown as feet and inches as well, so 170 cm reads as 5.58 ft and as 5 ft 6.93 in.

Each pair below has its own page with the formula, a worked example, a chart you can print and a scale that lines the two units up. For body height in feet and inches, use the height converter. Map coordinates have their own tool, the coordinates converter.