Length is where the metric and imperial worlds meet most often, and where the numbers are least negotiable: since the 1959 international yard and pound agreement, an inch is exactly 25.4 millimetres and a mile exactly 1609.344 metres. Those are definitions rather than measurements, so every converter here divides by the exact factor instead of multiplying by a rounded reciprocal.
Tools in this category
Kilometers to Miles
Convert kilometers to miles instantly in your browser. One mile is exactly 1.609344 kilometers, the factor fixed by the international yard and pound agreement.
Miles to Kilometers
Convert miles to kilometers in your browser. One mile is exactly 1.609344 kilometers, so the answer is a fixed ratio rather than an approximation.
Meters to Feet
Convert meters to feet instantly. A foot is exactly 0.3048 meters, so the conversion is a definition rather than a measurement.
Centimeters to Inches
Convert centimeters to inches in your browser. An inch is exactly 25.4 millimeters, fixed by international agreement in 1959.
Yards to Meters
Convert yards to meters in your browser. A yard is exactly 0.9144 meters — close to a meter, but not one.
Feet to Meters
Convert feet to meters in your browser. A foot is exactly 0.3048 meters, which makes the factor exact.
Millimeters to Inches
Convert millimeters to inches in your browser, with the fractional inch that workshops actually use.
Inches to Centimeters
Convert inches to centimeters in your browser. An inch is exactly 2.54 centimeters — an exact figure, not a rounded one.
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How these tools are built
Every tool in this category runs entirely in your browser: there is no upload, no account and no request to a server once the page has loaded. The numbers behind them are transcribed from the organisation that defines them — NIST for units, the W3C for web formats, the WHO for health measures — and each page names its source next to the formula. A tool whose reference values stop reproducing fails the build and does not ship, which is the whole reason the catalogue grows slowly.