About the length converter
Metric and imperial lengths are related by definition rather than by measurement: since 1959 an inch has been exactly 0.0254 metres, which makes every conversion here exact arithmetic rather than an approximation.
The most common confusion is between the two miles. A statute mile is 1,609.344 metres and is what road signs and running distances mean; a nautical mile is 1,852 metres, defined as one minute of latitude, and is used at sea and in the air.
Frequently asked questions
- Is anything I enter sent anywhere?
- No. Every conversion runs inside your browser. Nothing you type is uploaded, stored or logged, and the page keeps working with the network disconnected.
- How many centimetres are in an inch?
- Exactly 2.54. The inch has been defined as 0.0254 metres since the international yard and pound agreement of 1959, so this is a definition rather than a measurement.
- How do I convert kilometres to miles in my head?
- Multiply by 0.6 for a rough answer, or by 5 and divide by 8 for a closer one. The exact factor is 0.62137119.
- How accurate are these conversions?
- The factors are the exact legal definitions rather than rounded approximations - an inch is exactly 0.0254 metres and a pound exactly 0.45359237 kilograms - and results are shown to eight significant figures, which is more precision than any practical measurement carries.
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How your data is handled
Everything happens on your device. There is no upload, no storage and no logging. Closing the tab clears everything you entered.