How Many Centimeters in an Inch?
There are exactly 2.54 centimeters in one inch.
How to Convert Inches to Centimeters
To convert inches to centimeters, multiply by 2.54.
For example: 5 inches × 2.54 = 12.7 centimeters.
Why This Number Matters
Every spec sheet, size chart and tape measure that crosses between American and metric use depends on this one number. It is exact by international agreement, not an approximation.
A 15-inch laptop measures 38.1 centimeters diagonally, which is how it is advertised in Europe.
What People Get Wrong
Rounding to 2.5 cm looks harmless but is 1.6 percent short. Over a 60-inch measurement that is 2.4 centimeters, which is enough to make a curtain the wrong length.
Inches to Centimeters Conversion Table
| Inches (in) | Centimeters (cm) |
|---|---|
| 1 | 2.54 |
| 2 | 5.08 |
| 3 | 7.62 |
| 4 | 10.16 |
| 5 | 12.7 |
| 6 | 15.24 |
| 7 | 17.78 |
| 8 | 20.32 |
| 9 | 22.86 |
| 10 | 25.4 |
| 11 | 27.94 |
| 12 | 30.48 |
| 13 | 33.02 |
| 14 | 35.56 |
| 15 | 38.1 |
| 16 | 40.64 |
| 17 | 43.18 |
| 18 | 45.72 |
| 19 | 48.26 |
| 20 | 50.8 |
| 25 | 63.5 |
| 30 | 76.2 |
| 40 | 101.6 |
| 50 | 127 |
| 75 | 190.5 |
| 100 | 254 |
| 250 | 635 |
| 500 | 1,270 |
| 1,000 | 2,540 |
About These Units
The inch
The inch is exactly 2.54 centimeters by international agreement. Americans use it for screen sizes, lumber, rainfall, tire rims and body height together with feet.
The centimeter
A centimeter is one hundredth of a meter, or 10 millimeters. Most of the world lists body measurements, paper sizes and product dimensions in centimeters.
Definitions follow NIST Special Publication 811, Appendix B. See how we calculate for the exact values and rounding rules.
Frequently Asked Questions
Is 2.54 exact?
Yes. The 1959 international agreement defined the inch as exactly 2.54 centimeters, so there is no rounding in this conversion.
How many centimeters in 12 inches?
A foot is 12 inches, which is exactly 30.48 centimeters.
How many inches in a centimeter?
One centimeter is 0.393701 inches, a little under four tenths of an inch.
How many millimeters in an inch?
Exactly 25.4 millimeters.