Length Converter
Metric and imperial distance, converted into every unit at once.
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Decimals and fractions both work — 1.5 or 1 1/2.
1 cm = 0.3937008 in
1 cm in every other unit
- Nanometre (nm)10,000,000
- Micrometre (µm)10,000
- Millimetre (mm)10
- Metre (m)0.01
- Kilometre (km)0.00001
- Thou (mil) (thou)
One thousandth of an inch. Called a "mil" in US manufacturing, which is not a millimetre.
393.7008 - Inch (in)0.3937008
- Foot (ft)0.0328084
- Yard (yd)0.01093613
- Mile (mi)0.000006213712
- Nautical mile (nmi)
Exactly 1852 m by international agreement — longer than a statute mile.
0.000005399568 - Point (typographic) (pt)
The PostScript point: exactly 1/72 inch.
28.34646 - Pica (pc)2.362205
- CSS pixel (px)
A CSS reference pixel is 1/96 inch. It is a unit of layout, not of your screen’s hardware pixels.
37.79528 - Astronomical unit (au)6.684587e-14
- Light year (ly)1.057001e-18
- Parsec (pc)3.240779e-19
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How it works
To convert a length, enter the amount above and pick the unit it is in — the result appears in your chosen unit and in every other unit on the list at the same time, calculated in your browser with no upload.
Every unit here is defined by its exact size in metres, and each conversion goes through that base rather than through a table of pairs. That matters more than it sounds: a converter written as direct pairs needs a separate constant for every combination, and the moment one of them is corrected the others drift out of agreement. Going through a single base means each unit is written down once and every pair is derived from it.
The imperial and US figures are exact rather than rounded. Since the international yard and pound agreement of 1959, one yard is defined as exactly 0.9144 metres, which makes an inch exactly 25.4 millimetres and a mile exactly 1,609.344 metres by definition rather than by measurement. So converting 6 feet gives 1.8288 metres exactly, not a four-figure approximation of it.
A few units on the list are worth knowing apart. A nautical mile is 1,852 metres — about 15% longer than a statute mile — because it was defined as one minute of latitude rather than by land measure. A "mil" in US manufacturing is one thousandth of an inch, not a millimetre, and confusing the two is a factor of forty. A CSS pixel is exactly 1/96 inch and is a unit of layout, not a hardware pixel on your screen.
Nothing is sent anywhere. The whole unit table ships with the page and the arithmetic runs in your browser, which is why the results update as you type rather than after a round trip.
Centimetres to inches
One inch is exactly 2.54 centimetres, so centimetres convert to inches by dividing by 2.54. These are the values people look up most.
| Centimetres | Inches |
|---|---|
| 1 cm | 0.393701 in |
| 2 cm | 0.787402 in |
| 5 cm | 1.9685 in |
| 10 cm | 3.93701 in |
| 15 cm | 5.90551 in |
| 20 cm | 7.87402 in |
| 25 cm | 9.84252 in |
| 30 cm | 11.811 in |
| 50 cm | 19.685 in |
| 100 cm | 39.3701 in |
Feet to metres
A foot is exactly 0.3048 metres. Human heights are the most common reason to convert in this direction — 5 ft 10 in is 5.8333 feet, or 1.778 metres.
| Feet | Metres |
|---|---|
| 1 ft | 0.3048 m |
| 3 ft | 0.9144 m |
| 5 ft | 1.524 m |
| 5.5 ft | 1.6764 m |
| 6 ft | 1.8288 m |
| 6.5 ft | 1.9812 m |
| 10 ft | 3.048 m |
| 20 ft | 6.096 m |
| 50 ft | 15.24 m |
| 100 ft | 30.48 m |
Kilometres to miles
A kilometre is 0.621371 miles, so a 5 km race is a shade over three miles and a marathon’s 42.195 km is 26.2188 miles. The reverse — miles to kilometres — multiplies by 1.609344.
| Kilometres | Miles |
|---|---|
| 1 km | 0.621371 mi |
| 5 km | 3.10686 mi |
| 10 km | 6.21371 mi |
| 21.0975 km | 13.1094 mi |
| 42.195 km | 26.2188 mi |
| 50 km | 31.0686 mi |
| 100 km | 62.1371 mi |
FAQ
How many centimetres are in an inch?
Exactly 2.54. This is a definition rather than a measurement — the inch has been defined in terms of the metre since 1959, so the figure has no uncertainty in it.
How do I convert feet and inches to centimetres?
Multiply the feet by 30.48 and the inches by 2.54, then add them. 5 ft 9 in is 152.4 + 22.86 = 175.26 cm. Entering 5.75 in the converter above with feet selected gives the same answer.
Is a nautical mile the same as a mile?
No. A nautical mile is exactly 1,852 metres against the statute mile’s 1,609.344 — about 15% longer. It was defined as one minute of arc along a meridian, which is why it is used for sea and air navigation.
What is a "mil" in measurements?
In US manufacturing and engineering, one thousandth of an inch — 0.0254 mm. It is listed here as "thou" to keep it from being read as a millimetre, which it is not.
Are the conversions exact?
The constants are. Results are displayed to seven significant figures, so a value that terminates shows exactly and one that does not is rounded only at the last digit shown.