Loading...
Loading...
Convert metres, kilometres, centimetres, miles, yards, feet, and inches instantly. All calculations run in your browser.
The metre is the SI base unit of length, defined since 1983 as the distance light travels in a vacuum in 1/299,792,458 of a second. All metric length units derive from it by powers of ten: a kilometre is 1,000 metres, a centimetre is 0.01 metres, and a millimetre is 0.001 metres. This decimal structure makes metric arithmetic straightforward for science and engineering.
Imperial and US customary units follow a different hierarchy. One foot equals 12 inches; one yard equals 3 feet; one mile equals 5,280 feet (or 1,760 yards). The international foot is defined exactly as 0.3048 metres, which anchors the entire imperial system to the metric world. That definition gives 1 inch = 2.54 cm exactly, and 1 mile = 1.60934 km.
In practice, the choice of unit depends on context. Road distances in the United States and United Kingdom are measured in miles; the rest of the world uses kilometres. Building plans typically mix units: architects in the UK often work in metres and millimetres, while US plans use feet and fractional inches. Clothing sizes use centimetres in most countries and inches in the US and UK.
Manufacturing tolerances often require sub-millimetre precision. A machined part specified to ±0.05 mm needs to be checked against a tolerance of roughly ±0.002 inches if the tooling uses imperial gauges. Converting between systems without rounding errors is where a precise calculator saves time and prevents mistakes.
A few conversions appear constantly in everyday work. One mile equals exactly 1.609344 kilometres, so a 26.2-mile marathon is about 42.195 km. One foot equals exactly 30.48 centimetres, so a 6-foot person is 182.88 cm tall. One inch equals exactly 2.54 centimetres, which is the cornerstone of all US-to-metric length conversions.
The nautical mile sits outside the standard imperial system. It equals 1,852 metres exactly and was historically defined as one minute of arc along a meridian. It remains in use for aviation and maritime navigation because it ties directly to geographic coordinates.
How many centimetres are in a foot?
One foot equals exactly 30.48 centimetres. This is a fixed definition, not an approximation, because the international foot is defined as 0.3048 metres.
Is a US mile the same as a UK mile?
Yes. Both the United States and the United Kingdom use the international mile of 5,280 feet (1.609344 km). The older UK statute mile was the same length, so there is no practical difference.
What is a micrometre and when is it used?
A micrometre (µm) is one millionth of a metre. It is used in semiconductor manufacturing, optical coatings, and precision machining where tolerances are too fine to express in millimetres. For example, the wavelength of visible light ranges from roughly 380 µm to 700 µm.