The inches to cm conversion factor
One inch is defined as exactly 2.54 centimeters, so to convert inches to centimeters you multiply by 2.54: cm = inches × 2.54. For example, 12 inches × 2.54 = 30.48 cm. To reverse it, use the cm to inches calculator.
The 2.54 factor is exact by definition, agreed internationally in 1959, so nothing is lost in the conversion itself — only in the rounding you choose afterwards. It also means a foot is exactly 30.48 cm and a yard exactly 91.44 cm, which is why those figures never end in a repeating decimal.
How to convert inches to centimeters
Type your length in inches and the calculator multiplies by 2.54 to return centimeters. Useful for height, TV and monitor sizes, and DIY projects. Two decimal places is precise enough for most needs.
Worked examples: a 5 ft 9 in height is 69 inches, so 69 × 2.54 = 175.26 cm. A 27-inch monitor measures 27 × 2.54 = 68.58 cm along the diagonal. A quarter-inch drill bit is 0.25 × 2.54 = 0.635 cm, or 6.35 mm, which is why a 6 mm bit is close but not a substitute.
Imperial sizes are usually written as fractions, and that is where most errors creep in. Convert the fraction to a decimal first: 3/8 in is 0.375 in, so 0.375 × 2.54 = 0.95 cm. For a height in feet and inches, multiply the feet by 12 and add the inches before converting.
Inches to cm reference table
| Inches | Centimeters |
|---|---|
| 1 in | 2.54 cm |
| 6 in | 15.24 cm |
| 12 in | 30.48 cm |
| 36 in | 91.44 cm |
Rough mental check: an inch is about two and a half centimetres, so double the inches and add a quarter more. Ten inches is roughly 25 cm and 40 inches is roughly 100 cm. For larger measurements the feet to meters calculator is easier to read, and the cm to inches calculator reverses the direction by dividing by 2.54.
Frequently asked questions
- How many cm is 12 inches?
- 12 inches equals 30.48 cm (12 × 2.54).
- What is the inches to cm formula?
- cm = inches × 2.54, because 1 inch is exactly 2.54 cm.
- How many cm are in a foot?
- A foot is 12 inches, which is 30.48 cm.
- How do I convert cm back to inches?
- Divide centimeters by 2.54, or use the cm to inches calculator.
- Is a 27-inch monitor 27 inches wide?
- No — screen sizes are quoted as the diagonal, so a 27-inch display is 68.58 cm corner to corner and only about 60 cm wide in a 16:9 shape. Measure the diagonal before comparing a screen against a desk or a mount specification.