Length Unit Conversion
Quick answer: 1 inch = 2.54 cm, 1 foot = 30.48 cm = 0.3048 m, 1 yard = 0.9144 m, 1 mile = 1.609 km and 1 m = 100 cm = 1,000 mm.
Millimetres, centimetres, metres, kilometres, inches, feet, yards and miles – enter a value and see every conversion at once.
How the calculation works
Enter a length and choose the starting unit (e.g. cm, inch or foot). The table instantly shows the same length in millimetres, centimetres, decimetres, metres, kilometres, inches, feet, yards and miles.
Formula and assumptions
The base unit is the metre. Metric units differ by powers of 10 (1 m = 10 dm = 100 cm = 1,000 mm, 1 km = 1,000 m). Imperial units are defined exactly: 1 in = 0.0254 m, 1 ft = 12 in = 0.3048 m, 1 yd = 3 ft = 0.9144 m, 1 mi = 1,609.344 m.
More worked examples
- 250 cm to metres: 250 ÷ 100 = 2.5 m.
- 3/4 inch to mm: 0.75 × 25.4 = 19.05 mm.
- 6 feet tall: 6 × 30.48 = 182.88 cm.
- 5 miles to km: 5 × 1.609344 = 8.047 km.
Length units
| Unit | Metric | Imperial |
|---|---|---|
| 1 mm | 0.1 cm | 0.0393701 in |
| 1 cm | 10 mm | 0.393701 in |
| 1 m | 100 cm | 39.3701 in = 3.28084 ft |
| 1 km | 1,000 m | 0.621371 mi |
| 1 in | 2.54 cm | 1/12 ft |
| 1 ft | 30.48 cm | 12 in |
| 1 yd | 91.44 cm | 3 ft |
| 1 mi | 1.609344 km | 1,760 yd |
Common mistakes
- Converting mm to m by dividing by 100 instead of 1,000.
- Reading 5.6 feet as 5 feet 6 inches (5.6 ft = 5 ft 7.2 in).
- Confusing the statute mile (1.609 km) with the nautical mile (1.852 km).
Frequently asked questions
How many metres is one foot?
One foot is exactly 0.3048 m, or 30.48 cm. Ten feet are 3.048 m.
How do I convert cm to m?
Divide by 100: 250 cm = 2.5 m. To convert millimetres to metres, divide by 1,000.
How many inches are in a metre?
One metre is about 39.37 inches, or about 3.28 feet.
How do I convert feet and inches, e.g. 5′ 6″?
Convert each part and add them: 5 × 30.48 + 6 × 2.54 = 152.4 + 15.24 = 167.64 cm.
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