Convert length between millimetres, centimetres, metres, kilometres, inches, feet, yards, miles and nautical miles, with a full conversion table. Free, in your browser.
How the length converter works
Every unit is defined by its exact size in metres, the SI base unit of length: your value is multiplied into metres, then divided by the target unit's size. The imperial units have been tied to the metre by international agreement since 1959 — one inch is exactly 25.4 mm, one foot exactly 0.3048 m, one yard exactly 0.9144 m and one mile exactly 1,609.344 m — so the conversions are exact definitions, not approximations. The nautical mile, used at sea and in aviation, is defined as exactly 1,852 m. Results are rounded to six significant digits for display.
metres = value × from.toBase → result = metres ÷ to.toBaseFrequently asked questions
Is anything I enter uploaded anywhere?
No. The conversion is simple arithmetic that runs locally in your browser. Nothing you type is sent to a server, logged or stored — only the value and selected units appear in the URL so you can share a link to the exact conversion.
How exact are the metric–imperial conversions?
Exact. The international yard and pound agreement of 1959 defined the inch, foot, yard and mile directly in metres — 1 inch = 25.4 mm with no remainder. Any rounding you see is display rounding to six significant digits, not measurement error.
What is a nautical mile and why is it different from a mile?
A nautical mile is exactly 1,852 m — originally one minute of latitude, which makes chart navigation arithmetic easy at sea and in the air. A land (statute) mile is 1,609.344 m, so a nautical mile is about 15% longer.
Last updated: 8 July 2026
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