CM to Inches Converter
Centimetres to inches and back, with fractions and feet.
Type in either box. Inches also take fractions and feet: 1 1/2, 3/4, 5'7", 5 ft 7 in.
Centimetres to inches: the one number you need
An inch is exactly 2.54 centimetres. Not roughly — exactly, by international agreement since 1959, when the US, the UK and the Commonwealth fixed the inch to the metric system. So converting is a single step either way:
- cm → inches: divide by 2.54.
30 cm ÷ 2.54 = 11.811 in - inches → cm: multiply by 2.54.
12 in × 2.54 = 30.48 cm
Because the factor is exact, inches to centimetres never needs rounding: any whole number of inches comes out as a finite decimal. The other direction does — 1 cm is 0.393700787… inches, recurring — which is why this converter shows four decimal places and the nearest tape-measure fraction alongside.
Fractions, feet and the tape measure
Rulers and tape measures in inches are divided in halves, quarters, eighths and sixteenths, not tenths, so a decimal like 11.811 in is hard to find on one. The fraction readout rounds to the nearest 1/16" by default — the finest mark on most tape measures — and you can switch it to 1/8" for rough work or 1/32" for machinist rules. When the fraction is rounded it is shown with ≈, so you always know whether you are looking at an exact value.
For anything over a foot, the feet-and-inches readout does the second step people usually do in their heads: 170 cm is 66.93 in, which is 5 ft 6.9 in — quoted as 5′7″ for a height.
Typing inches the way you write them
The inch box accepts what you would actually write down: 12, 12.5, a European decimal comma like 12,5, mixed fractions such as 1 1/2 or 1½, plain fractions like 3/4, and feet with inches as 5'7", 5' 7.5 or 5 ft 7 in. Everything is converted as you type; there is no button to press.
Quick estimates without a calculator
- Inches to cm: multiply by 2.5. You will be 1.6% low — 10 in comes out as 25 cm against the exact 25.4.
- cm to inches: multiply by 4 and divide by 10. You will be 1.6% high — 50 cm comes out as 20 in against the exact 19.69.
- Feet to cm: one foot is 30.48 cm, so call it 30 and add 1.6%.
Common conversions
Each of these has its own page with the working, a table of nearby values and, for screens and heights, what the number actually means.
Frequently asked questions
How many centimetres are in an inch?
Exactly 2.54. The international inch was defined as 25.4 mm in 1959, and every country that uses inches has used that definition since — there is no "US inch" and "UK inch" to choose between any more.
How many inches are in a centimetre?
0.3937 inches, rounded. The exact value is 1 ÷ 2.54 = 0.393700787…, a recurring decimal, so every cm-to-inch result is rounded somewhere. This converter keeps four decimal places, which is far finer than any ruler can show.
Why does the fraction say ≈?
Because the length does not fall exactly on a 1/16" mark. 30 cm is 11.811 in, and the nearest sixteenth is 11 13/16" (11.8125 in) — 0.04 mm away, close enough for any tape measure, but not equal. Lengths that land exactly on a mark, like 3.81 cm = 1 1/2", show without the ≈.
Is the ruler on this page life size?
No, and no web page can promise that: a browser does not know how many physical pixels per inch your screen has, so "1 inch" in CSS is a nominal 96 pixels that might be anything from 1.5 to 3 cm on real glass. The ruler is drawn to scale between its two edges, so it shows how centimetres and inches compare, not their absolute length.
Does it work offline?
Yes. The conversion is a few lines of JavaScript running in your browser; nothing is sent anywhere. Once the page has loaded you can disconnect and keep using it.