How to Convert Inches to CM
To convert inches to centimetres, multiply by 2.54. This guide shows worked examples and how to handle fractions and feet.
More inch and cm tools
How to use the How to Convert Inches to CM
- Take the measurement in inches.
- Multiply it by 2.54.
- For feet and inches, convert everything to inches first.
How it works
One inch is defined as exactly 2.54 cm, so cm = inches × 2.54 and inches = cm ÷ 2.54.
Method: multiply by 2.54
An inch is defined as exactly 2.54 cm, so centimetres = inches × 2.54. There is no rounding in the factor, so the answer is exact.
4 inches to cm
cm = 4 × 2.54cm = 10.16- In millimetres: 101.6 mm
11 inches to cm
cm = 11 × 2.54cm = 27.94- In millimetres: 279.4 mm
24 inches to cm
cm = 24 × 2.54cm = 60.96- In millimetres: 609.6 mm
Doing it without a calculator
Split 2.54 into easy parts: multiply by 2, then by 0.5, then by 0.04, and add. For 11 inches: 22 + 5.5 + 0.44 = 27.94 cm. For a quick estimate, multiply by 2.5 (double, then add half): 11 × 2.5 = 27.5 cm, about 0.4 cm low.
Fractions and decimals of an inch
Convert the fraction to a decimal first: 3/8″ = 0.375″, and 0.375 × 2.54 = 0.9525 cm. For mixed values like 7 1/2″, use 7.5 × 2.54 = 19.05 cm. The fraction to decimal converter helps with awkward fractions.
Feet and inches
Change feet to inches (× 12), add the inches, then multiply by 2.54. 6 ft 2 in = 74 in = 187.96 cm. The feet and inches to cm calculator does this in one step.
Checking your answer
Divide your centimetres by 2.54 — you should get back the inches you started with. The centimetre figure should also be about two and a half times the inch figure; if it is smaller, you divided instead of multiplying.
Practice questions
| # | Inches | Answer |
|---|---|---|
| 1 | 3″ | Show7.62 cm |
| 2 | 9.5″ | Show24.13 cm |
| 3 | 14″ | Show35.56 cm |
| 4 | 22″ | Show55.88 cm |
| 5 | 30″ | Show76.2 cm |
| 6 | 48″ | Show121.92 cm |
Why you will need it
Inches are everywhere in American products, recipes, plans and screen sizes, while the rest of the world measures in centimetres. Whether you are following a US sewing pattern, buying a TV or filling in a form, one exact fact — 1 inch = 2.54 cm — is all you need. For the other direction, use the cm to inches converter.
Frequently asked questions
What is the formula for inches to cm?
cm = inches × 2.54.
Why multiply by 2.54?
Because one inch is defined as exactly 2.54 centimetres.
How do you convert inches to cm in your head?
Multiply by 2.5 (double it and add half); the answer is about 1.6% low.
How do I convert cm back to inches?
Divide by 2.54.