What it does
This converter changes a length between centimetres and inches, in either direction. Type a number and the answer appears as you type; the swap button flips which unit you are converting from. Nothing is sent to a server — the arithmetic runs in your browser.
How it works
There is one number to remember: 1 inch is exactly 2.54 centimetres. That is a definition, not a measurement — since 1959 the inch has been fixed at 2.54 cm by international agreement, so the conversion is exact and never rounds at source.
To go from centimetres to inches you divide by 2.54; to go the other way you multiply by 2.54. The two operations undo each other, which is why converting a value and then converting it back returns the number you started with.
Worked example
Take 2.54 cm. Dividing by the factor gives 2.54 ÷ 2.54 = 1, so 2.54 cm is exactly 1 inch. This is the cleanest case to picture, because 2.54 cm is the very length one inch is defined to be.
Common uses
- Height: reading a height given in centimetres on a passport or medical form when you think in feet and inches, or the reverse.
- Screen and TV sizes: screens are sold by their diagonal in inches, but fit into spaces measured in centimetres.
- Sewing, knitting and DIY: patterns and timber are often quoted in one unit while your tape measure reads the other.
- UK and US contexts: swapping between metric measurements and the inches still used for many everyday items on both sides of the Atlantic.
Frequently asked
How many centimetres are in an inch?
Exactly 2.54. One inch equals 2.54 cm, so ten inches is 25.4 cm and a foot (12 inches) is 30.48 cm.
Is 2.54 exact, or rounded?
It is exact. The inch is defined as 2.54 cm under the 1959 international yard and pound agreement, so there is no longer error in the figure — any rounding you see is only in how the answer is displayed.
How do I convert my height?
First turn your height into total inches, then multiply by 2.54. For example, 5 ft 9 in is (5 × 12) + 9 = 69 inches, and 69 × 2.54 = 175.26 cm. To go from centimetres back to feet and inches, divide by 2.54 to get inches, then split off whole feet.