Length Converter: mm, cm, m, km, Inches, Feet, Yards, Miles

How length conversion works

Each unit is defined as an exact number of meters, so converting is a matter of multiplying into meters and dividing back out:

Result = Value × (meters per “from” unit) ÷ (meters per “to” unit)

Example: 5 kilometers to miles is 5 × 1000 ÷ 1609.344 = 3.106855961 miles. In the other direction, 1 mile is exactly 1.609344 km.

The exact definitions used

Since the international yard and pound agreement of 1959, the inch has been defined as exactly 25.4 millimeters, and the foot, yard and mile follow from it. The nautical mile, used at sea and in aviation, is defined as exactly 1852 meters. None of the factors below are rounded.

Length units and their exact value in meters
Unit	In meters	Status
1 millimeter	0.001 m	SI prefix (1/1000)
1 centimeter	0.01 m	SI prefix (1/100)
1 meter	1 m	SI base unit
1 kilometer	1,000 m	SI prefix (×1000)
1 inch	0.0254 m	Exact by definition
1 foot	0.3048 m	Exact by definition
1 yard	0.9144 m	Exact by definition
1 mile	1,609.344 m	Exact by definition
1 nautical mile	1,852 m	Exact by definition

Handy reference values

Common length conversions
From	To
1 inch	2.54 cm
1 foot (12 in)	30.48 cm
1 yard (3 ft)	0.9144 m
1 mile (1760 yd)	1.609344 km
1 meter	3.280839895 ft
1 kilometer	0.6213711922 mi
10 km (a common race distance)	6.213711922 mi
Marathon, 42.195 km	26.21875746 mi

Which countries use which units?

Almost every country uses the metric system for official and everyday measurement. The United States uses US customary units (inches, feet, miles) for most everyday purposes, and the United Kingdom still uses miles and yards on road signs and often uses feet and inches for personal height. Aviation worldwide commonly gives altitude in feet, and shipping and aviation use nautical miles for distance.

Common questions

Is a UK mile different from a US mile?

No. Both use the international mile of exactly 1609.344 m. The US survey mile, an older unit very slightly longer (about 1609.347 m), was officially retired by NIST at the end of 2022 and is not used for everyday distances.

How precise are the results?

Results are shown to 10 significant digits, which is far more than a tape measure can resolve. Round to a sensible number of digits for your purpose: a room measured to the nearest centimeter does not become more accurate when converted to inches with six decimals.

Can I convert feet and inches together?

Yes, use the feet to meters converter, which accepts heights such as 5 ft 10 in, or the cm to inches converter, which shows results in feet and inches.