How to convert length units
Pick the unit you have in From and the unit you want in To, type a value and press Convert. The result is shown to up to 12 significant digits. A length cannot be negative, so negative values are rejected.
How the conversion works
Every unit is stored as a number of meters. The converter multiplies your value by the meters in the source unit and divides by the meters in the target unit, so any pair of units converts in one step. The meter itself is defined as the distance light travels in vacuum in 1/299,792,458 of a second.
US and imperial units are tied to the meter by the international yard and pound agreement of 1959, which made the yard exactly 0.9144 m. That fixes the foot at 0.3048 m, the inch at 25.4 mm and the mile (5,280 feet) at 1,609.344 m. These are exact definitions, not approximations.
| Length | Equals | Exact or rounded |
|---|---|---|
| 1 inch | 2.54 cm | exact |
| 1 foot | 0.3048 m | exact |
| 1 yard | 0.9144 m | exact |
| 1 mile | 1.609344 km | exact |
| 1 nautical mile | 1.852 km | exact |
| 1 centimeter | 0.393701 in | rounded |
| 1 meter | 3.28084 ft | rounded |
| 1 kilometer | 0.621371 mi | rounded |
Worked examples
- 5 ft 10 in to centimeters: 5 × 12 + 10 = 70 in, and 70 × 2.54 = 177.8 cm.
- 10 km to miles: 10,000 m ÷ 1,609.344 ≈ 6.2137 mi.
- 1.75 m to feet and inches: 1.75 ÷ 0.3048 ≈ 5.7415 ft. Keep the 5 whole feet and convert the rest: 0.7415 × 12 ≈ 8.9 in, so about 5 ft 8.9 in. The converter returns a single unit, so this last split is done by hand.
- 3/8 inch to millimeters: 0.375 × 25.4 = 9.525 mm.
Feet to meters
| ft | m | cm |
|---|---|---|
| 1 | 0.3048 | 30.48 |
| 2 | 0.6096 | 60.96 |
| 3 | 0.9144 | 91.44 |
| 5 | 1.524 | 152.4 |
| 6 | 1.8288 | 182.88 |
| 10 | 3.048 | 304.8 |
| 50 | 15.24 | 1524 |
| 100 | 30.48 | 3048 |
Inches to centimeters
| in | cm | mm |
|---|---|---|
| 0.5 | 1.27 | 12.7 |
| 1 | 2.54 | 25.4 |
| 2 | 5.08 | 50.8 |
| 6 | 15.24 | 152.4 |
| 12 | 30.48 | 304.8 |
| 24 | 60.96 | 609.6 |
| 36 | 91.44 | 914.4 |
Miles and kilometers
| mi | km |
|---|---|
| 1 | 1.609 |
| 5 | 8.047 |
| 10 | 16.093 |
| 26.2 | 42.165 |
| 100 | 160.934 |
| km | mi |
|---|---|
| 1 | 0.621 |
| 5 | 3.107 |
| 10 | 6.214 |
| 42.195 | 26.219 |
| 100 | 62.137 |
Units that are easy to confuse
- International foot and US survey foot. Before 1959 the United States defined the yard as 3600/3937 m, and that older foot (1200/3937 m, about 0.3048006 m) stayed in use for land surveying. It is two parts per million longer than the international foot: about 3.2 mm over a mile, but 2 feet on a coordinate of 1,000,000 feet. The US survey foot was deprecated at the end of 2022, yet older deeds and state plane coordinates still use it, which is why it is listed separately.
- Mile and nautical mile. The nautical mile used at sea and in aviation is exactly 1,852 m, about 1.1508 statute miles. It was originally based on one minute of latitude.
- Mil and millimeter. A mil (or thou) is a thousandth of an inch, 25.4 µm, and is common for coating and sheet thickness. It is not a millimeter: one millimeter is about 39.37 mils.
- Micron. The old name for the micrometer (µm), one millionth of a meter. The ångström (Å) is 0.1 nm.
- Surveying and nautical units. A chain is 66 ft (22 yd), a furlong is 10 chains and a mile is 8 furlongs. A rod is a quarter of a chain, 16.5 ft, and a fathom, used for water depth, is 6 ft, or 1.8288 m. These units are based on the international foot here, and the league is taken as 3 miles, although historical leagues varied from place to place.
- Light-year. Despite the name, it is a distance: the path light travels in a Julian year of 365.25 days, exactly 9,460,730,472,580,800 m, or about 9.461 trillion km. The astronomical unit is fixed at 149,597,870,700 m, and a parsec is about 206,265 au, or 3.2616 light-years.
Common mistakes
- Rounding the factor too early. Using 3.28 ft per meter makes 1,000 m come out as 3,280 ft instead of about 3,280.84 ft. Convert with the full factor and round only the final answer.
- Reading decimal feet as feet and inches. 5.5 ft is 5 ft 6 in, not 5 ft 5 in, because a foot has 12 inches, not 10.
- Using a length factor for area or volume. A meter is about 3.28 ft, but a square meter is about 10.76 square feet. Use the area converter or the volume converter for those.
Frequently asked questions
How many feet are in a meter?
About 3.28084. Exactly, one meter is 1 ÷ 0.3048 feet, a number that never ends, so any printed value is rounded.
Why is an inch exactly 2.54 cm?
Because the 1959 agreement defined it that way. Before then, the US and UK inches differed very slightly from each other and from 25.4 mm.
How do I convert a height like 6 ft 2 in?
Turn it into one unit first: 6 × 12 + 2 = 74 in. Then convert inches to centimeters, which gives 187.96 cm.
Which foot should I use for a US land survey?
Check the document or its coordinate system. The survey foot was common in US surveying until its deprecation, and new work is expected to use the international foot. Over 100 feet the two differ by only about 0.06 mm, so the choice matters for large coordinates and long distances rather than for a single lot line.
Supported units
- Kilometer (km)
- Meter (m)
- Decimeter (dm)
- Centimeter (cm)
- Millimeter (mm)
- Micrometer (µm)
- Nanometer (nm)
- Picometer (pm)
- Ångström (Å)
- Mile (mi)
- Yard (yd)
- Foot (ft)
- Inch (in)
- Mil (thousandth of an inch) (mil)
- Nautical mile (NM)
- League (3 miles) (lea)
- Furlong (fur)
- Chain (ch)
- Rod (rd)
- Fathom (ftm)
- US survey foot (ft (US survey))
- US survey mile (mi (US survey))
- Astronomical unit (au)
- Light-year (ly)
- Parsec (pc)