What this length converter does
This tool converts any length or distance between the eight units people use most often: millimeters (mm), centimeters (cm), meters (m) and kilometers (km) from the metric system, and inches (in), feet (ft), yards (yd) and miles (mi) from the imperial and US customary systems. It works in both directions — metric to imperial or imperial to metric — and it recalculates instantly as you type, change a unit, or press the Swap button. Below the main answer you will also find your measurement expressed in all eight units at once, which is handy when a plan, pattern or product listing uses a unit you did not expect.
Everyday length conversions come up constantly: a TV or monitor sold by its diagonal inches, a room measured in feet that must be matched against furniture listed in centimeters, a 5K run described in kilometers, sewing patterns, lumber, height on a medical form, or the size of a suitcase for an airline. Because the two systems grew up independently, few of the conversions are round numbers, and doing them in your head invites mistakes. This converter uses the exact international definitions, so the figure you get here is the figure a tape measure, airline or engineer would use.
How to use it
- Type the measurement into the From box.
- Choose the unit you are converting from in the first dropdown, and the unit you want in the second dropdown.
- Read the answer in the blue result box. Use Swap to reverse the direction without retyping, and check the table below the result if you need the same length in any other unit.
The conversion factors (so you can check our math)
All conversions on this page are built from exact definitions. Since 1959, the inch has been defined as exactly 25.4 millimeters, which makes every imperial-to-metric length conversion exact rather than approximate:
| Unit | Equals (in meters) | Useful equivalents |
|---|---|---|
| Millimeter (mm) | 0.001 m | 10 mm = 1 cm |
| Centimeter (cm) | 0.01 m | 2.54 cm = 1 inch |
| Meter (m) | 1 m | 1 m ≈ 3.28084 feet |
| Kilometer (km) | 1,000 m | 1 km ≈ 0.621371 miles |
| Inch (in) | 0.0254 m | 12 inches = 1 foot |
| Foot (ft) | 0.3048 m | 3 feet = 1 yard |
| Yard (yd) | 0.9144 m | 1,760 yards = 1 mile |
| Mile (mi) | 1,609.344 m | 5,280 feet = 1 mile |
The formula is always the same: multiply your value by the factor for the unit you have, then divide by the factor for the unit you want. The converter does exactly that, and only rounds the final number for display.
Worked examples
- A 55-inch TV: 55 × 2.54 = 139.7 cm across the diagonal — useful when a stand or wall mount is listed in centimeters.
- A 5K run: 5 km × 0.621371 = about 3.11 miles.
- A person's height: 5 feet 9 inches is 69 inches, and 69 × 2.54 = 175.26 cm, or 1.7526 m.
- A room: a 12 ft × 10 ft room is 3.6576 m × 3.048 m — the numbers you need when flooring is sold by the square meter.
Tips for accurate measuring
A converter can only be as accurate as the measurement you feed it. Measure twice, use the same starting point both times, and for flexible items like fabric or waistlines use a soft tape that follows the curve. When a manufacturer says "about" or gives a range, convert the whole range rather than a single number. And remember that lumber and many building materials are sold by nominal sizes — a "2×4" is not actually 2 inches by 4 inches — so convert the real, finished dimensions when fit matters.
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54. The inch has been defined as 25.4 millimeters since 1959, so inch–centimeter conversions are exact.
How do I convert feet to meters?
Multiply feet by 0.3048. Six feet, for example, is 1.8288 meters.
How many feet are in a mile?
5,280 feet, or 1,760 yards. A mile is exactly 1.609344 kilometers.
Is a US yard the same as a British yard?
Yes. Since the 1959 international agreement, the yard is exactly 0.9144 meters in the US, the UK and everywhere else that uses it.
Private by design: this conversion happens in your browser. Your measurements are never sent to or stored on a server.