Units covered
Metre, kilometre, centimetre, millimetre and micrometre on the metric side; mile, yard, foot and inch on the imperial side; plus the nautical mile used in aviation and shipping. Conversions run off fixed metre-based factors (1 mile = 1609.344 m, 1 inch = 0.0254 m, and so on), so the result is exact — there's no rounding error building up from chaining conversions.
Common questions
How many decimal places is the result accurate to?
The math is done in full floating-point precision; only the display is rounded for readability. For a measurement you need to the millimetre or beyond, the "All Conversions" table below gives every unit at once so you can cross-check.
Why do US and UK sources give slightly different mile or yard values?
They don't, for these units — the international mile, yard and foot were standardized in 1959 and are identical in both. You'll only see a difference with the older US survey foot, which this converter doesn't use.
Can I convert a very large or very small number?
Yes — there's no practical limit; the field accepts scientific values fine (JavaScript's number precision holds up to roughly 15–17 significant digits, well past what a physical measurement would ever need).