Inch to cm Converter
Convert inches to centimetres and back, using the exact factor of 2.54.
Slik bruker du Inch to cm
- 01
Enter the number of inches you want to convert.
- 02
Leave the units on in and cm, or pick mm, m or ft instead.
- 03
Read or copy the result, or press swap to convert the other way.
The inch is exactly 2.54 cm
One inch is exactly 2.54 centimetres. That word, exactly, is doing real work: the factor is a definition, not a measurement, so it carries no rounding error at any number of decimal places.
Before 1959 the inch differed slightly between countries, and a US inch was not quite a British inch. The international yard and pound agreement fixed the yard at exactly 0.9144 metres, which makes the inch exactly 0.0254 metres, and the discrepancy disappeared.
Going the other way, one centimetre is 0.3937007874 inches. That figure does repeat forever, because it is the reciprocal of an exact number rather than a defined one.
Common inch values in centimetres
1 inch is 2.54 cm. 2 inches is 5.08 cm. 5 inches is 12.7 cm. 10 inches is 25.4 cm.
12 inches, one foot, is 30.48 cm. 24 inches is 60.96 cm. 36 inches, one yard, is 91.44 cm.
For a rough estimate without a calculator, multiply by 2.5 and add a bit: 10 inches is a little over 25 cm, and 40 inches is a little over 100 cm.
Where the inch still shows up
Screen sizes are quoted as the diagonal in inches, so a 27 inch monitor measures 68.58 cm corner to corner. Wheel and rim diameters, bicycle frames, and pipe threads follow the same pattern.
In each case the inch figure is a product name as much as a measurement, which is why it survives in countries that otherwise use the metric system throughout.
Ofte stilte spørsmål
How many cm is one inch?
Exactly 2.54 cm. This is not a rounded approximation. The inch was defined as exactly 0.0254 metres by the international yard and pound agreement of 1959, and every country that uses the inch has used that definition since.
How do I convert cm back to inches?
Press the swap button, or pick cm as the source unit. One centimetre is 0.3937007874 inches, so a quick mental estimate is to divide by 2.5 and subtract a little.
Can I enter fractional inches like 1/2 or 3/8?
Enter them as decimals. Half an inch is 0.5, three eighths is 0.375, and three quarters is 0.75. The tool takes a decimal value rather than a fraction.
Why are screens and wheels still measured in inches?
Some industries standardised on the inch before metrication and never switched, because the numbers appear on decades of tooling, catalogues and packaging. Screen diagonals, wheel and rim diameters, and pipe threads are the common examples.
Is anything uploaded?
No. The conversion is arithmetic that runs in your browser, so nothing is sent to a server and the page keeps working offline once it has loaded.
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