Length Converter
Distance - from the nanometer to the light year.
Enter a value above to convert between cm and in.
How to convert length units
Every length conversion goes through the meter, the SI base unit: you multiply by the ratio of the two units' sizes. The inch is defined as exactly 2.54 centimeters, which gives the everyday rules inches = cm ÷ 2.54 and cm = inches × 2.54. Longer distances follow the same pattern - miles = km ÷ 1.609344 and km = miles × 1.609344 - because one mile is defined as exactly 1,609.344 meters.
Worked example
To convert 30 centimeters to inches, divide by 2.54: 30 ÷ 2.54 = 11.811 in. Going the other way, a 12-inch foot is 12 × 2.54 = 30.48 cm, and a 5-kilometer run works out to 5 ÷ 1.609344 = 3.107 mi.
How many centimeters are in an inch?
One inch equals exactly 2.54 centimeters. One foot equals 30.48 centimeters (0.3048 m), one yard equals 0.9144 meters, one mile equals 1.609344 kilometers, and one nautical mile equals 1,852 meters. These are exact definitions fixed by the international yard-and-pound agreement of 1959 and the SI - not rounded approximations.
When you'll use a length converter
Length conversion comes up wherever metric and imperial units meet: reading a height given in feet and inches when you think in centimeters, following a sewing pattern or recipe in millimeters, checking paper and screen sizes, comparing travel distances in miles and kilometers, or reading engineering drawings. The table above lists your value in all 11 supported units at once, so you can scan the equivalent you need without converting twice.