📏 Cm to Inches Converter
Convert centimetres to inches and back. The exact factor, a table of the values people look up most, and what each unit is actually used for.
Converting centimetres to inches
One centimetre is 0.3937007874 inches, and one inch is 2.54 centimetres.
inches = centimetres × 0.3937007874
Getting the precision right
One inch is exactly 2.54 cm by definition, so the conversion carries no measurement uncertainty at all — it is a definition, not an approximation. Dividing by 2.5 instead of 2.54 is 1.6% high, which over a 180 cm height is nearly 3 cm.
Where each unit is used
Centimetres are standard almost everywhere for body measurements, paper, furniture and clothing. Inches hold on in the United States for nearly everything, and internationally for screen sizes, wheel diameters, pipe fittings and photographic print sizes, which is why even metric countries quote a 27-inch monitor.
Values worth knowing
| cm | in |
|---|---|
| 1 | 0.393701 |
| 2.54 | 1 |
| 5 | 1.9685 |
| 10 | 3.93701 |
| 15 | 5.90551 |
| 20 | 7.87402 |
| 30 | 11.811 |
| 50 | 19.685 |
| 100 | 39.3701 |
| 180 | 70.8661 |
A 180 cm person is 70.9 inches, or 5 ft 11 in. An A4 sheet is 21 by 29.7 cm, which is 8.3 by 11.7 inches. A 30 cm ruler is just under 12 inches.
Where the two units came from
The inch was defined at various times as three barleycorns laid end to end, and as the width of a man's thumb — the same ambiguity that made international trade difficult enough to force a resolution. In 1959 the United States, United Kingdom, Canada, Australia, New Zealand and South Africa agreed on exactly 25.4 millimetres, replacing several slightly different national inches. The centimetre needed no such treaty: it was defined as one hundredth of the metre from the start.
Round the result to the precision your own work needs. These converters carry the full factor, which is useful for checking but rarely what you want to write down.
The natural follow-ups are the feet to cm, for what this figure feeds into, and the miles to km, for the closely related case.
Frequently Asked Questions (FAQs)
How many centimetres are in an inch?
Exactly 2.54. This has been the international definition since 1959, so unlike most unit conversions there is no rounding involved at all.
How do I convert cm to feet and inches?
Divide the centimetres by 2.54 to get total inches, then divide by 12 for the feet and keep the remainder as inches. 180 cm is 70.87 inches, which is 5 feet and 10.9 inches.
Why are screens measured in inches?
Because the display industry standardised on American units early and never changed. The figure is the diagonal, not the width, which is why two screens with the same inch rating can be noticeably different shapes.