Length Converter

It converts your value through meters as a single canonical base unit: your value is first converted to meters using the From unit's exact conversion factor, then that meters value is converted into the To unit using its own exact factor. This two-step approach avoids the accumulated rounding error a direct unit-to-unit table can introduce as more units are added.

Metric units (millimeters, centimeters, meters, kilometers) scale by powers of ten and are the standard in science and most countries. Imperial units (inches, feet, yards, miles) use traditional, non-decimal ratios (12 inches per foot, 3 feet per yard, 5,280 feet per mile) and remain in everyday use in the United States. This calculator converts freely between both systems.

The meter is the SI (International System of Units) base unit of length, and every unit this calculator supports - metric or imperial - has an exact, internationally defined conversion factor to meters. Routing every conversion through one common base unit keeps the calculation simple and exact, rather than needing a separate formula for every possible pair of units.

Yes. Enter any decimal value (e.g. 2.5) and it converts normally. Results are shown to 4 decimal places by default; a very small result that would otherwise round to 0 is shown with additional decimal places instead, so a genuinely nonzero result is never displayed misleadingly as zero.

No. A length cannot be negative, so the calculator rejects a negative value rather than returning a meaningless negative result. Zero is accepted, since a length of zero is valid.