Length Converter (m, cm, inch, ft, mile…)
Convert length between millimetres, centimetres, metres, kilometres, inches, feet, yards, and miles — one value into every unit, with a reference table.
Length conversion reference
| 1 unit | mm | m | in | ft |
|---|---|---|---|---|
| 1 mm | 1 | 0.001 | 0.0393701 | 0.00328084 |
| 1 cm | 10 | 0.01 | 0.393701 | 0.0328084 |
| 1 m | 1 000 | 1 | 39.3701 | 3.28084 |
| 1 km | 1 000 000 | 1 000 | 39 370.1 | 3 280.84 |
| 1 in | 25.4 | 0.0254 | 1 | 0.0833333 |
| 1 ft | 304.8 | 0.3048 | 12 | 1 |
| 1 yd | 914.4 | 0.9144 | 36 | 3 |
| 1 mi | 1 609 340 | 1 609.34 | 63 360 | 5 280 |
Converting length units
Length is measured in two families of units — the metric system built on the metre, and the imperial / US system of inches, feet, yards, and miles. Converting between them all comes down to one fixed anchor: an inch is exactly 2.54 centimetres. Everything else follows from that. Enter a value and its unit and this tool shows it in every unit at once.
The relationships worth remembering
Within metric, each step is a factor of ten: 10 mm in a cm, 100 cm in a metre, 1000 m in a kilometre. Within imperial, 12 inches make a foot, 3 feet a yard, and 1760 yards (5280 feet) a mile. The two cross over through the inch = 2.54 cm definition, from which a metre works out to about 3.281 feet and a mile to about 1.609 kilometres.
Worked example
A 5 km run is 5 × 1000 = 5000 m, or 5000 / 0.3048 ≈ 16 404 feet — about 3.107 miles. Going the other way, a 6-foot person is 6 × 0.3048 = 1.829 m, or 182.9 cm. Because the conversions are exact ratios, the result is precise, not rounded.
Related
Working with wire rather than distance? TheAWG wire gauge calculator converts gauge to diameter and cross-section.
Exact conversions, approximate measurements
Every conversion here is exact by definition — an inch is exactly 25.4 mm and a foot exactly 0.3048 m, fixed by international agreement since 1959 — so there is no uncertainty in the arithmetic at all. The limit is entirely in your measurement. A length taken with a tape to the nearest millimetre cannot produce a result meaningful to four decimal places, however many the display shows. Carry full precision through intermediate steps and round once at the end.