1 inch = 2.54 centimetres
Exactly 2.54 centimetres to the inch, and the exactness is deliberate: the 1959 international yard and pound agreement chose a value that made imperial and metric lengths commensurable rather than approximately related.
Formula cm = in × 2.54
Type in either field — the other updates on every keystroke. Need other units? Open the full length converter.
| Inch | Centimetre |
|---|---|
| 1 in | 2.54 cm |
| 2 in | 5.08 cm |
| 3 in | 7.62 cm |
| 4 in | 10.16 cm |
| 5 in | 12.7 cm |
| 10 in | 25.4 cm |
| 15 in | 38.1 cm |
| 20 in | 50.8 cm |
| 25 in | 63.5 cm |
| 50 in | 127 cm |
| 100 in | 254 cm |
| 500 in | 1270 cm |
| 1000 in | 2540 cm |
| Centimetre | Inch |
|---|---|
| 1 cm | 0.393701 in |
| 2 cm | 0.787402 in |
| 3 cm | 1.181102 in |
| 4 cm | 1.574803 in |
| 5 cm | 1.968504 in |
| 10 cm | 3.937008 in |
| 15 cm | 5.905512 in |
| 20 cm | 7.874016 in |
| 25 cm | 9.84252 in |
| 50 cm | 19.685039 in |
| 100 cm | 39.370079 in |
| 500 cm | 196.850394 in |
| 1000 cm | 393.700787 in |
| Situation | From | To |
|---|---|---|
| Ruler | 12 in | 30.48 cm |
| US letter paper width | 8.5 in | 21.59 cm |
| Waist size | 34 in | 86.36 cm |
| 27-inch monitor | 27 in | 68.58 cm |
| Six-foot person | 72 in | 182.88 cm |
Multiply by 2.5 and accept a result about 1.6% low. For 12 in: 30 cm, against an exact 30.48 cm.
Screen sizes, clothing, furniture and paper are quoted in inches in the US. A 27-inch monitor is 68.58 cm diagonally, US letter paper is 21.59 cm wide, and a 6-foot person (72 in) is 182.88 cm tall.
Rounding to 2.5 stacks up over long lengths: 100 in is 254 cm, not 250. Keep the exact 2.54 for woodworking and tailoring.
The 1959 international yard and pound agreement defined the inch as exactly 25.4 mm, ending small differences between US and UK inches. The US survey foot, a slightly different legacy unit used in land surveying, was retired at the end of 2022.
Related guides: Imperial vs metric: differences and quick conversion tricks