Length converter
Convert millimetres, centimetres, metres, and kilometres to and from inches, feet, yards, and miles, instantly and entirely in your browser. Nothing is uploaded.
The amount to convert. Leave empty or non-numeric for no result.
Metric and imperial, one exact table
Length has two systems people switch between constantly: metric (mm, cm, m, km) and imperial (inches, feet, yards, miles). Because each imperial unit is defined as an exact metric value — an inch is precisely 0.0254 m — this converter moves between them without the rounding errors you get from remembered approximations like “an inch is about 2.5 cm”. Pick any two units and convert in either direction.
Runs entirely on your device
There is no server, no account, and no upload. The math is a few lines of JavaScript that execute in your browser, so the tool works offline and your figures stay private, whether you are converting a height, a running distance, or a part dimension.
Frequently asked questions
- Does this send my data anywhere?
- No. The converter is plain JavaScript that runs entirely in your browser. There is no upload, no network request, and no account. The numbers you type never leave your device.
- How many centimetres are in an inch?
- Exactly 2.54. The inch is defined as 0.0254 metres, so 1 in = 2.54 cm, 1 ft = 30.48 cm, and 1 yd = 91.44 cm. The converter uses these exact definitions, so metric-to-imperial steps are not approximations.
- How many feet are in a mile?
- 5280. A mile is 1609.344 metres, a yard is 0.9144 metres, and a foot is 0.3048 metres, which gives exactly 5280 feet or 1760 yards per mile.
- Which units are supported?
- Metric — millimetres, centimetres, metres, and kilometres — and imperial — inches, feet, yards, and miles. You can convert between any two in either direction.
- How precise are the results?
- Imperial units are defined as exact metric values (1 inch ≡ 0.0254 m), so conversions are exact within floating-point limits. Long fractional results are rounded to twelve significant figures for readability.