Length Converter
Convert cm to inches, mm to inches, inches to cm and every other length unit in one place. Metric and imperial both ways, with the answer appearing as you type. It runs in your browser, so there is nothing to install and nothing to sign up for.
Working with file sizes instead? Use KB to MB.
Quick answer
One centimetre is 0.3937 inches, so to convert cm to inches you divide by 2.54. Type your figure into the box above and the answer appears immediately. The same tool handles mm to inches, inches to cm, metres, feet, yards, kilometres and miles, in either direction.
Converting length in three steps
Enter your number
Type into the left box. Decimals are fine, and the result updates as you type.
Pick the two units
Centimetres and inches are preset. Change either dropdown for any other pair.
Read or swap
The answer is on the right. Press the swap arrows to reverse the direction.
inches = cm ÷ 2.54The exact definition since 1959. One inch is 25.4 mm, so the factor never rounds.
Why cm to inches is a division by 2.54
The inch has been defined as exactly 25.4 millimetres since the international agreement of 1959, which makes 2.54 centimetres. That is a definition, not a measurement, so no rounding creeps in. Divide by 2.54 to go from centimetres to inches, multiply by 2.54 to come back. Every other length pair on this page is built on the same fixed relationship.
mm to inches and inches to mm
Millimetres are where precision work lives, so mm to inches comes up constantly in engineering drawings, 3D printing and anything involving screws or tolerances. Divide millimetres by 25.4. Going the other way, inches to mm means multiplying by 25.4. Because the factor is exact, a value like 0.5 inches lands on precisely 12.7 mm rather than something that needs rounding.
inches to cm without the guesswork
Height and clothing are the everyday case. A person listed at 5 foot 9 is 175.26 cm, and a 32 inch waist is 81.28 cm. Converting inches to cm is a multiplication by 2.54, but the tool above also takes feet and inches together, so you can enter 5 and 9 rather than working out 69 inches first.
km to miles for travel and running
A kilometre is 0.621371 miles, which is why a 5 km race is a little over 3.1 miles and a marathon is 42.195 km. Converting km to miles matters most when reading road signs abroad or comparing running distances between apps that use different systems. Enter the figure above and switch the dropdowns to kilometres and miles.
Common length conversions
| From | To | Result |
|---|---|---|
| 1 cm | inches | 0.3937 in |
| 10 cm | inches | 3.937 in |
| 30 cm | inches | 11.811 in |
| 1 mm | inches | 0.03937 in |
| 1 inch | cm | 2.54 cm |
| 12 inches | cm | 30.48 cm |
| 1 m | feet | 3.2808 ft |
| 1 km | miles | 0.6214 mi |
| 1 mile | km | 1.6093 km |
Why choose our length converter
Free and unlimited
No account, no sign up, no daily cap.
Runs in your browser
Nothing is sent to a server, so it works offline once loaded.
Every unit in one place
Swap either side and the whole category is in the dropdowns.
Instant on mobile
Results update as you type, with no page reload.
Length questions
How do I convert cm to inches by hand?+
Is 2.54 an approximation?+
Can I enter feet and inches together?+
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