Length Converter

A length converter turns one unit of distance into another — 1 metre is 3.28084 feet, 1 inch is exactly 2.54 centimetres, and 1 mile is exactly 1.609344 kilometres. Two of those figures are not measurements at all but definitions: since 1959 the inch and the mile have been defined in terms of the metre, agreed internationally so that engineering drawings from different countries fit together. That is why this page can convert between metres, feet, inches, miles, yards and millimetres without any figure being approximate. Pick the units, type an amount, and the answer appears as you type. Everything runs in your browser and nothing is sent anywhere.

How to use it

1. Choose the unit you have and the unit you want.
2. Type the amount. The result updates as you type.
3. Every conversion goes through metres internally, so converting inches to miles is as exact as inches to centimetres.
4. Answers are shown to six significant figures, which keeps small conversions from collapsing to zero — 1 millimetre in kilometres is 0.000001, not nothing.

Examples

• 6 feet = 1.8288 metres.
• 1 mile = 1.609344 kilometres, exactly.
• 1 inch = 2.54 centimetres, exactly.
• A 26.2-mile marathon = 42.1648 kilometres.

Frequently asked questions

How many centimetres are in an inch?

Exactly 2.54. This is not a measurement anyone took — it is a definition, agreed in 1959 by the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa in what is usually called the international yard and pound agreement. Before it, the American inch and the British inch differed very slightly, which was tolerable for carpentry and not tolerable for aircraft parts made in one country and fitted in another. Because the inch is defined from the metre, every conversion on this page between imperial and metric length is exact rather than rounded.

How do I convert my height from feet and inches to centimetres?

Turn the whole height into inches first, then multiply by 2.54. Someone who is 5 feet 9 inches is 5 x 12 + 9 = 69 inches, and 69 x 2.54 = 175.26 centimetres. Doing it in one step is where people go wrong: converting the feet and the inches separately and adding the results works, but only if you convert both, and it is easy to convert the feet and forget the leftover inches. If you are entering a height here, put the whole thing in inches.

How many kilometres is a mile?

1.609344 kilometres, exactly, and going the other way 1 kilometre is 0.621371 miles. The rough version most people carry around — multiply by 1.6, or take the miles and add about 60% — is accurate to well under a percent and perfectly good for reading a road sign. It stops being good enough for anything cumulative: over a marathon, using 1.6 instead of 1.609344 loses about 240 metres, which is most of a lap of a running track.

Why is a nautical mile different from a mile?

Because it measures something different. A nautical mile is exactly 1,852 metres and was originally one minute of latitude — one sixtieth of a degree — which makes it enormously convenient at sea, where you navigate on a sphere using charts marked in degrees. A distance in nautical miles can be read straight off the latitude scale at the edge of a chart. The ordinary statute mile, at 1,609.344 metres, comes from Roman and later English land measurement and has no relationship to the size of the Earth. Both are on this page and they are about 15% apart, which is far too much to confuse.

Are these conversions exact or rounded?

The conversion factors are exact; the answer shown is rounded for reading. The inch, the foot, the yard and the mile are all defined from the metre by international agreement, so no accuracy is lost in the conversion itself. What you see is rounded to six significant figures, which is far finer than any tape measure and keeps very small and very large answers readable. If you need the full precision for something like machining, use the defining factors: 25.4 millimetres to the inch, and 1,609.344 metres to the mile.