The factor
An inch has been exactly 2.54 cm since 1959, so inches = cm ÷ 2.54, which is the same as cm × 0.393700787402. For a quick estimate, 10 cm is a little under 4 inches.
Common lengths
Worked out from the factor and rounded to two decimal places:
| Centimetres | Inches |
|---|---|
| 1 cm | 0.39 in |
| 2.5 cm | 0.98 in |
| 10 cm | 3.94 in |
| 15 cm | 5.91 in |
| 21 cm | 8.27 in |
| 30 cm | 11.81 in |
| 50 cm | 19.69 in |
| 100 cm | 39.37 in |
A sheet of A4 paper is 21 cm by 29.7 cm, which is 8.27 by 11.69 inches.
Height in feet and inches
Divide the inches by 12 for feet, and what is left over stays as inches: 175 cm is 68.9 inches, which is 5 ft 8.9 in.
Questions
How many inches is 30 cm?
11.81 inches, just under a foot. A foot is 30.48 cm.
Can I paste a number with commas?
Yes. Commas and spaces are ignored, so 1,200 is read as 1200 cm, which is 472.44 inches. Use a point for decimals: 12.7 cm is exactly 5 inches.