Length Conversion Chart: Metric and Imperial Units
November 9, 2026
Every length conversion between metric and imperial comes back to one number: an inch is exactly 2.54 centimeters. Since 1959, when the US, the UK and several Commonwealth countries agreed on a common yard, the inch, foot, yard and mile have all been defined in terms of the meter. So the factors below are exact, not approximations.
Imperial to metric
| Unit | Metric value |
|---|---|
| 1 inch (in) | 2.54 cm, or 25.4 mm |
| 1 foot (ft) = 12 in | 30.48 cm, or 0.3048 m |
| 1 yard (yd) = 3 ft | 0.9144 m |
| 1 mile (mi) = 5,280 ft | 1.609344 km |
Metric to imperial
| Unit | Imperial value |
|---|---|
| 1 millimeter (mm) | 0.03937 in |
| 1 centimeter (cm) | 0.3937 in |
| 1 meter (m) | 3.2808 ft, or 1.0936 yd |
| 1 kilometer (km) | 0.62137 mi |
These are rounded. Dividing by an exact number like 2.54 gives a decimal that never ends, so going from metric to imperial always involves some rounding.
Converting within each system
Metric lengths are powers of ten of the meter, so converting within metric only moves the decimal point:
- 10 millimeters = 1 centimeter
- 100 centimeters = 1 meter
- 1,000 meters = 1 kilometer
Imperial units follow no pattern: 12 inches to a foot, 3 feet to a yard and 1,760 yards to a mile.
Worked examples
- Height. 5 feet 10 inches is 70 inches, and 70 × 2.54 = 177.8 cm.
- Running races. A 5K is 3.11 miles and a 10K is 6.21 miles. A marathon is 42.195 km, which is 26.22 miles.
- Screens. A 55-inch TV measures 55 × 2.54 = 139.7 cm across the diagonal.
- Sprints. 100 meters is 328.08 feet, or 109.36 yards.
- Ceilings. An 8-foot ceiling is 8 × 0.3048 = 2.4384 m, so about 2.44 m.
Quick mental conversions
When you don't need precision:
- Inches to centimeters. Multiply by 2.5. The answer comes out about 2% low.
- Meters to feet. Multiply by 3.3. The answer comes out about 0.6% high.
- Miles to kilometers. Multiply by 1.6. The answer comes out about 0.6% low.
- Kilometers to miles. Use neighboring Fibonacci numbers: 5 km is about 3 miles, 8 km is about 5 miles and 13 km is about 8 miles. The exact figures are 3.11, 4.97 and 8.08 miles.
Mistakes to avoid
- Reading feet and inches as a decimal. 5.10 feet is not 5 feet 10 inches. It's 5 feet 1.2 inches. Convert the inches separately: 10 ÷ 12 = 0.833, so 5 feet 10 inches is 5.833 feet.
- Rounding too early. Round once, at the end. Using 1.6 instead of 1.609344 puts you about 9 meters short for every mile.
- The US survey foot. Some older US land records use the survey foot, defined as 1200/3937 m. It's about 2 parts per million longer than the standard foot. The US retired it at the end of 2022, but older surveys still use it.
Convert any length
The length converter handles every pair. You can also go straight to inches to centimeters, centimeters to inches, feet to meters, meters to feet, kilometers to miles or miles to kilometers.