Length Unit Converter
Convert length and distance between metric and imperial units — millimetres to miles — using exact internationally defined factors.
How it works
metres = value × factor(from) · result = metres ÷ factor(to) (1 in = 0.0254 m, 1 mi = 1609.344 m)
Every length converts through a single base unit — the metre — so any pair of units is just two multiplications. The imperial units are defined exactly in metric terms: an inch is precisely 0.0254 m and a mile is 1609.344 m, both fixed by international agreement in 1959. Nautical miles are separate again, defined as exactly 1852 m for marine and aviation navigation.
Worked example
Convert 1 mile to kilometres: 1 × 1609.344 = 1609.344 m, then 1609.344 ÷ 1000 = 1.609344 km. So a mile is about 1.61 km.
Frequently asked questions
How many kilometres are in a mile?
Exactly 1.609344 km, since a mile is defined as 1609.344 metres. For quick mental math, multiply miles by 1.6 (or divide km by 1.6 to get miles).
Why is a nautical mile different from a regular mile?
A nautical mile (1852 m) is based on one minute of latitude along a meridian, which makes it natural for navigation. A statute mile (1609.344 m) comes from an older land measure, so the two are unrelated in size.
Are inches and feet exact in metric?
Yes. Since 1959 the international inch is defined as exactly 0.0254 m, which makes a foot exactly 0.3048 m and a yard exactly 0.9144 m — there is no rounding involved.
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This calculator is for educational purposes. Double-check important results before acting on them.