Length Converter
Convert between metric and imperial lengths with exact factors.
Convert lengths between millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles. Uses exact international definitions — 1 inch is exactly 2.54 cm — so results are precise enough for engineering homework and DIY alike.
How it's calculated
Every unit converts through meters with its exact factor: 1 inch = 0.0254 m, 1 foot = 0.3048 m, 1 yard = 0.9144 m, 1 mile = 1609.344 m. The result is value × factor[from] ÷ factor[to].
Frequently asked questions
How do I convert kilometers to miles?
Enter 5, choose km → mi: about 3.107 miles. The exact factor is 1 km = 0.621371 mi.
How many centimeters are in an inch?
Multiply by 2.54 — or just use this tool. 12 inches is exactly 30.48 cm.
Are these conversions exact?
Yes. An international inch is defined as exactly 2.54 cm, and a mile as exactly 1609.344 m, so every conversion here is exact to full precision.