Inches to Centimeters
Convert inches to centimeters in your browser. An inch is exactly 2.54 centimeters — an exact figure, not a rounded one.
cm = in × 2.54
NIST SP 811 (2008), Appendix B.8 — inch (in) to meter (m) = 2.54 E−02
Screens, tyres, pipe fittings and waist sizes are quoted in inches in some markets and centimeters in others, so this conversion turns up whenever something is bought across a border. The number behind it is exact: since 1959 an inch has been defined as exactly 25.4 millimeters, chosen so that neither system has to round.
How it is calculated
cm = in × 2.54
The factor is exact, so the conversion loses nothing. Going the other way, dividing by 2.54 is also exact — but multiplying by 0.3937 is not, and that approximation drifts as measurements grow.
Source: NIST SP 811 (2008), Appendix B.8 — inch (in) to meter (m) = 2.54 E−02
Common values
| inches | centimeters |
|---|---|
| 1 | 2.54 |
| 2 | 5.08 |
| 6 | 15.24 |
| 10 | 25.4 |
| 12 | 30.48 |
| 15.6 | 39.624 |
| 24 | 60.96 |
| 27 | 68.58 |
| 32 | 81.28 |
| 40 | 101.6 |
| 55 | 139.7 |
Questions people ask
- How big is a 55 inch television?
- The diagonal is 139.7 centimeters. That is the diagonal and not the width, so a 55 inch set is roughly 122 centimeters across — worth checking before measuring the wall it has to fit.
- Why is the inch defined in millimeters?
- Because the two systems had to agree on something, and the metre was already the international standard. Before 1959 the imperial and US inches differed by a fraction of a millionth, which mattered in precision engineering. Fixing the inch at exactly 25.4 millimeters ended that.
- Do I round the result?
- For anything you cut, no — carry the full figure and round at the end. For clothes and furniture, rounding to the nearest half centimeter is finer than the tolerance of the thing being measured anyway.
Found a problem, or want more?
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