How does length conversion work?
Every length unit is a fixed multiple of the meter, so converting between any two units takes two steps. The tool first turns your number into meters, then divides by the size of the target unit in meters.
The units in this converter are millimeters, centimeters, meters, kilometers, inches, feet, yards and miles. The factors it uses are exact definitions: an inch is 0.0254 m, a foot is 0.3048 m, a yard is 0.9144 m and a mile is 1,609.344 m.
So the general rule is: result = value x (size of the From unit in meters) / (size of the To unit in meters). Results are rounded to six decimal places.
When you need to switch between metric and imperial
Most people reach for a length converter when two systems meet: a product spec in centimeters that you need in inches, a road distance in miles that you want in kilometers, or a room measurement in feet for a metric floor plan.
It also helps with travel, DIY projects, sewing patterns, school homework and reading international shipping dimensions.
For other quantities, the same site has a weight converter and an area converter, which is handy if you are converting a floor plan and need both lengths and square footage.
How to convert a length
- Type your number in the From box.
- Pick the starting unit from the dropdown under it.
- Pick the target unit in the dropdown under To.
- The converted value appears in the To box straight away.
Worked example one: 5 miles to kilometers. 5 x 1,609.344 = 8,046.72 meters, and dividing by 1,000 gives 8.04672 km.
Worked example two: 10 inches to centimeters. 10 x 0.0254 = 0.254 meters, and dividing by 0.01 gives 25.4 cm.
The two dropdowns can both be set to the same unit, in which case the value is returned unchanged.
Limits and things to check
The converter works one value at a time. It does not parse mixed inputs such as 5 ft 7 in, so convert the feet and inches parts separately and add them, or turn everything into inches first (5 ft is 60 in).
Because results are rounded to six decimal places, very tiny values converted into very large units can display as 0. Pick a smaller target unit if that happens.
The unit list is fixed. Nautical miles, light years and older units such as furlongs are not included. If the input box is empty or not a valid number, the result box stays blank.