How to use the length converter
- Type the number you want to convert into the value box.
- Choose the unit you are starting from, and the unit you want to end up in.
- Press Convert. The result appears instantly below the button.
- Read the rate line to see how many target units are in one source unit, and the formula line to see the exact math behind the answer.
How length conversion works
Every length unit can be expressed as a number of meters, so this tool converts everything through meters as a common ground. It multiplies your value by the meters factor of the source unit, then divides by the meters factor of the target unit. That single two-step calculation handles metric and imperial units alike, which is why switching from inches to kilometers works exactly the same way as switching from yards to centimeters.
Because the factors are fixed constants, the result is exact rather than an estimate. The only limit on precision is how many digits your number has.
The meters factor of each unit
| Unit | Equals (in meters) |
|---|---|
| Millimeter (mm) | 0.001 m |
| Centimeter (cm) | 0.01 m |
| Meter (m) | 1 m |
| Kilometer (km) | 1,000 m |
| Inch (in) | 0.0254 m |
| Foot (ft) | 0.3048 m |
| Yard (yd) | 0.9144 m |
| Mile (mi) | 1,609.344 m |
Metric versus imperial in everyday use
Metric units scale by powers of ten, so moving between millimeters, centimeters, meters and kilometers just shifts a decimal point. Imperial units are based on older, irregular ratios — twelve inches to a foot, three feet to a yard, 1,760 yards to a mile. A converter removes the need to remember any of those ratios, which is especially handy when you are reading a recipe in one system, ordering materials in another, or checking the dimensions of a product sold in a foreign market. Because the meter is now defined in terms of the speed of light, every imperial unit is ultimately tied back to it, which is exactly why a meters-based factor table gives exact conversions across both systems.