How the Length Converter Works
Length is measured in different units around the world. Most countries use millimeters, meters and kilometers. The United States and the United Kingdom still use inches, feet, yards and miles for many things, such as height, road distance and room sizes. The Length Converter changes a length from one unit into another, so you can follow a measurement from another country, compare distances or check a size.
What you enter
- The value: a number, which can have decimals.
- The unit you have (From): millimeters, centimeters, meters, kilometers, inches, feet, yards or miles.
- The unit you want (To): any of the same units.
How the conversion works
Every unit has a fixed size in meters. The converter turns your length into meters, and then turns the meters into the unit you chose:
meters = value x meters in the From unit result = meters / meters in the To unit
These are the exact sizes of the units, set by international agreement:
| Unit | Size in meters |
|---|---|
| 1 millimeter (mm) | 0.001 |
| 1 centimeter (cm) | 0.01 |
| 1 meter (m) | 1 |
| 1 kilometer (km) | 1,000 |
| 1 inch (in) | 0.0254 |
| 1 foot (ft) | 0.3048 |
| 1 yard (yd) | 0.9144 |
| 1 mile (mi) | 1,609.344 |
An inch is exactly 2.54 centimeters. A foot is exactly 12 inches, a yard is exactly 3 feet, and a mile is exactly 1,760 yards, or 5,280 feet.
A worked example
You want to change 10 meters into feet.
| Step | Value |
|---|---|
| Meters to feet (10 / 0.3048) | 32.8084 ft |
The same 10 meters in other units:
| Unit | Amount |
|---|---|
| Millimeters | 10,000 mm |
| Centimeters | 1,000 cm |
| Kilometers | 0.01 km |
| Inches | 393.7008 in |
| Feet | 32.8084 ft |
| Yards | 10.9361 yd |
| Miles | 0.006214 mi |
Feet to meters
| Feet | Meters |
|---|---|
| 1 | 0.3048 |
| 5 | 1.524 |
| 6 | 1.8288 |
| 10 | 3.048 |
| 50 | 15.24 |
| 100 | 30.48 |
Miles to kilometers
| Miles | Kilometers |
|---|---|
| 1 | 1.609 |
| 5 | 8.047 |
| 10 | 16.093 |
| 26.2 (marathon) | 42.165 |
| 50 | 80.467 |
| 100 | 160.934 |
Chart: the small units in centimeters
Each bar shows how long the unit is. A meter is the longest of these four, and a yard is a little shorter.
1 inch ▏ 2.54 cm 1 foot ████████████ 30.48 cm 1 yard █████████████████████████████████████ 91.44 cm 1 meter ████████████████████████████████████████ 100 cm
Chart: a mile and a kilometer
A mile is longer than a kilometer. One mile is about 1.6 kilometers, so a kilometer is about 62% of a mile.
1 km █████████████████████████ 1,000 m 1 mile ████████████████████████████████████████ 1,609 m
Doing it by hand
- Inches to centimeters: multiply by 2.54. So 70 in is 177.8 cm.
- Feet to meters: multiply by 0.3048. So 6 ft is 1.83 m.
- Meters to feet: multiply by 3.281. So 100 m is 328.1 ft.
- Miles to kilometers: multiply by 1.609. So 5 mi is 8.05 km.
- Kilometers to miles: multiply by 0.6214. So 10 km is 6.21 mi.
- Yards to meters: multiply by 0.9144. So 100 yd is 91.44 m.
A quick estimate: to change miles into kilometers, multiply by 1.6. For 50 miles, 50 x 1.6 is 80 km, and the exact answer is 80.47 km. To go back, multiply the kilometers by 0.6. For 100 km that gives 60 miles, and the exact answer is 62.14 miles.
Height in feet and inches
People often give height as feet and inches. Change the feet into inches (12 for each foot), add the inches, and then multiply by 2.54. For 5 ft 10 in, that is 5 x 12 + 10 = 70 inches, and 70 x 2.54 = 177.8 cm.
Where these conversions are used
- Height and clothing: a person's height, or a size in a pattern or a shop.
- Home and building work: room sizes, furniture, screens, pipes and timber.
- Travel and sport: road signs in miles or kilometers, running and cycling distances. A marathon is 42.195 km, or 26.22 miles.
- School and science: unit conversion exercises, and maps and scales.
- Shopping online: sizes of products from another country.
Tips
- Check the unit twice. A mistake between feet and meters, or miles and kilometers, is the most common error. A meter is 3.3 times longer than a foot.
- Use the same unit for all the numbers in a calculation, such as the length and width of a room, before you work out the area.
- Do not confuse an inch with a centimeter. An inch is 2.54 times longer than a centimeter.
- Small values need more digits. A millimeter is a very small number of kilometers (0.000001), so the result may need many decimal places.
What this converter does not include
- Nautical miles, light-years and other special units.
- Area and volume. Use an area or a volume converter for those.
- The old US survey foot, which differs from the international foot by about 2 parts in a million.
This tool gives an estimate for general information only. For building, engineering or legal work that needs an exact measure, use a calibrated measuring tool and follow the official rules.