Length converter
Since 1959 the inch has been exactly 2.54 cm, which fixes the foot at 0.3048 m and the mile at 1609.344 m. The rule under the result shows both scales side by side so you can see how big the answer is.
30 cm = 11.81102362 in
Formula: in = cm ÷ 2.54
30 cm in every length unit
- millimetre
- metre
- kilometre
- inch
- foot
- yard
- mile
- nautical mile
Popular length conversions
How it works
Where the number 1.609344 comes from
Nothing is measured here. Every step below is a definition written into law or into the SI.
1 mi
Every length unit, defined
Each unit expressed in metres, with its exact definition and source.
| Unit | In m | Definition | Source |
|---|---|---|---|
| millimetre (mm) | 0.001 | 1 mm = 0.001 m | BIPM SI Brochure |
| centimetre (cm) | 0.01 | 1 cm = 0.01 m | BIPM SI Brochure |
| metre (m) | 1 | SI base unit, fixed by the speed of light | BIPM SI Brochure |
| kilometre (km) | 1,000 | 1 km = 1000 m | BIPM SI Brochure |
| inch (in) | 0.0254 | 1 in = 2.54 cm exactly | NIST SP 811, App. B (1959 yard & pound agreement) |
| foot (ft) | 0.3048 | 1 ft = 12 in = 0.3048 m | NIST SP 811, App. B (1959 yard & pound agreement) |
| yard (yd) | 0.9144 | 1 yd = 3 ft = 0.9144 m | NIST SP 811, App. B (1959 yard & pound agreement) |
| mile (mi) | 1,609.344 | 1 mi = 5280 ft = 1609.344 m | NIST SP 811, App. B (1959 yard & pound agreement) |
| nautical mile (nmi) | 1,852 | 1 nmi = 1852 m exactly | NIST SP 811; International Hydrographic Conference 1929 |
Questions
How many centimetres are in an inch?
Exactly 2.54 cm. This was agreed internationally in 1959 and is not rounded.
How do I convert my height in cm to feet and inches?
Pick centimetres to feet; the result shows decimal feet and the feet-and-inches reading, e.g. 180 cm = 5.905 ft = 5 ft 10.9 in.
How many feet are in a metre?
1 m = 3.280 839 895 ft (1 ÷ 0.3048).
What is the difference between a mile and a nautical mile?
A statute mile is 1609.344 m. A nautical mile is 1852 m, originally based on one minute of latitude, and is used at sea and in aviation.
Does the US survey foot still matter?
NIST retired the US survey foot at the end of 2022. It differed from the international foot by 2 parts per million, which matters only for large land surveys.