Length Converter
Convert between mm, cm, m, km, inches, feet, yards, and miles.
Why use this tool?
Convert lengths between metric and imperial units, for example meters to feet or kilometers to miles, using exact international conversion factors.
How to use it
- Enter the value you want to convert.
- Choose the unit you have and the unit you want.
- Read the result instantly; use the ⇄ button to swap direction.
How the conversion works
Every length is first converted to meters and then to the unit you want, so any pair of units uses the same exact factors. The imperial units have been defined in terms of the meter since the 1959 international yard and pound agreement: one inch is exactly 2.54 centimeters, one foot is exactly 0.3048 meters, one yard is exactly 0.9144 meters and one mile is exactly 1,609.344 meters.
Because these factors are exact, conversions are not approximations. The only rounding is in how many decimal places are displayed, which matters for very small or very large values (for example converting a few millimeters into miles).
Worked examples
Height: 5 feet 9 inches is 69 inches. 69 × 2.54 = 175.26 cm, which most people round to 175 cm. Going the other way, 180 cm ÷ 2.54 = 70.87 inches, or 5 feet 10.9 inches.
Running: a 5 km race is 5,000 ÷ 1,609.344 = 3.107 miles, and a marathon of 26.2 miles is about 42.16 km (the official distance is 42.195 km).
DIY and printing: an A4 sheet is 210 × 297 mm, which is 8.27 × 11.69 inches. US Letter is 8.5 × 11 inches, or 215.9 × 279.4 mm, so the two are close but not interchangeable.
Common mistakes
Mixing feet and inches as decimals is the most frequent error: 5.9 feet is not 5 feet 9 inches. 5.9 feet is 5 feet 10.8 inches. Convert feet-and-inches to plain inches first (feet × 12 + inches), then convert.
A US survey mile and a nautical mile are different units from the statute mile used here. A nautical mile is exactly 1,852 meters and is used in aviation and shipping; this converter uses the ordinary (international) mile.
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54. The inch has been defined as 25.4 mm since 1959, so the conversion never changes.
How do I convert my height in feet and inches to centimeters?
Multiply the feet by 12, add the inches, and convert that total in inches to centimeters. For 6 ft 1 in: 73 inches × 2.54 = 185.42 cm.
Why does a mile convert to such an odd number of meters?
The mile comes from old English units (5,280 feet), and the foot was later fixed at 0.3048 m. 5,280 × 0.3048 = 1,609.344 m exactly.