Last updated: November 8, 2026
To convert inches to cm, multiply the number of inches by 2.54. One inch is exactly 2.54 centimeters (25.4 millimeters), so 10 inches equals 25.4 cm and 12 inches equals 30.48 cm. To go the other way, divide centimeters by 2.54. The 2.54 factor is an exact definition, not a rounded estimate.
Contents
- Inches to cm formula
- How to convert inches to cm, step by step
- Inches to cm conversion chart
- Inches to cm for height (feet and inches)
- How to convert cm to inches
- How to convert inches to cm in your head
- Why is an inch exactly 2.54 cm?
- Frequently asked questions
Inches to cm formula
The inches to cm formula is:
centimeters = inches × 2.54
The U.S. National Institute of Standards and Technology (NIST) states that the inch is “exactly equivalent to 25.4 mm,” and 25.4 mm is 2.54 cm (NIST, SI Units – Length). NIST’s official table of conversion factors lists the same value, 2.54 × 10−2 meter per inch, as exact (NIST Guide to the SI, Appendix B.9).
Because the factor is exact, any rounding comes only from how many decimal places you choose to keep in your answer. For most everyday measurements, one or two decimal places is plenty.
How to convert inches to cm, step by step
- Write down the length in inches. Convert any fraction to a decimal first, for example 3/8 inch = 0.375 inch.
- Multiply that number by 2.54.
- Round the result to the precision you need and label it “cm.”
- For millimeters, multiply inches by 25.4 instead, or move the decimal point in the centimeter answer one place to the right.
Example: a 15.6-inch laptop screen is 15.6 × 2.54 = 39.624 cm, or about 39.6 cm measured diagonally. A 3/8-inch bolt is 0.375 × 25.4 = 9.525 mm.
Inches to cm conversion chart
This inches to cm chart covers common fractions, rulers, yardsticks and tape-measure lengths. Values are exact to three decimal places.
| Inches | Centimeters |
|---|---|
| 1/4 inch | 0.635 cm |
| 1/2 inch | 1.27 cm |
| 1 inch | 2.54 cm |
| 2 inches | 5.08 cm |
| 3 inches | 7.62 cm |
| 4 inches | 10.16 cm |
| 5 inches | 12.7 cm |
| 6 inches | 15.24 cm |
| 8 inches | 20.32 cm |
| 10 inches | 25.4 cm |
| 12 inches | 30.48 cm |
| 15 inches | 38.1 cm |
| 18 inches | 45.72 cm |
| 20 inches | 50.8 cm |
| 24 inches | 60.96 cm |
| 30 inches | 76.2 cm |
| 36 inches | 91.44 cm |
| 48 inches | 121.92 cm |
| 50 inches | 127 cm |
| 100 inches | 254 cm |
A standard 12-inch ruler is 30.48 cm, and a 36-inch yardstick is 91.44 cm, which matches the legal yard of 0.9144 meters.
Inches to cm for height (feet and inches)
Height is the most common reason people search for inches to cm height conversions. First turn feet into inches (feet × 12), add the remaining inches, then multiply the total by 2.54. One foot is exactly 30.48 cm.
| Height | Total inches | Centimeters |
|---|---|---|
| 4′10″ | 58 in | 147.32 cm |
| 5′0″ | 60 in | 152.4 cm |
| 5′2″ | 62 in | 157.48 cm |
| 5′4″ | 64 in | 162.56 cm |
| 5′6″ | 66 in | 167.64 cm |
| 5′7″ | 67 in | 170.18 cm |
| 5′8″ | 68 in | 172.72 cm |
| 5′10″ | 70 in | 177.8 cm |
| 6′0″ | 72 in | 182.88 cm |
| 6′2″ | 74 in | 187.96 cm |
| 6′4″ | 76 in | 193.04 cm |
For example, 5 feet 10 inches is (5 × 12) + 10 = 70 inches, and 70 × 2.54 = 177.8 cm. If you are also converting body weight, see our guide to converting pounds to kilograms, and use both numbers in our step-by-step BMI calculation guide.
How to convert cm to inches
To convert cm to inches, divide by 2.54:
inches = centimeters ÷ 2.54 (or centimeters × 0.3937)
So 100 cm is 100 ÷ 2.54 = 39.37 inches, and 50 cm is about 19.69 inches. To turn a centimeter height into feet and inches, divide by 2.54, then divide the inches by 12. The whole number is feet and the remainder is inches. For example, 180 cm ÷ 2.54 = 70.87 inches, which is 5 feet 10.9 inches.
How to convert inches to cm in your head
A quick mental shortcut is to multiply by 2.5 and then add a little extra:
- Step 1: multiply inches by 2.5 (double the number, then add half of the original). For 20 inches, that is 40 + 10 = 50.
- Step 2: add 4 percent of the original inches (inches × 0.04). For 20 inches, that is 0.8.
- Result: 50 + 0.8 = 50.8 cm, which is exact.
For a rough estimate, “inches times 2.5” is within about 1.6 percent of the true answer. Going the other way, centimeters times 0.4 gives a fast, slightly high estimate in inches. The same estimate-then-correct approach works for distance in our km to miles conversion guide.
Why is an inch exactly 2.54 cm?
Before 1959, the United States and the United Kingdom used slightly different yards, so their inches did not quite match. In 1958, a conference of English-speaking nations agreed to define the yard and pound in metric terms, making the international yard exactly 0.9144 meters. NIST explains that the American yard was shortened and the imperial yard was lengthened as a result, and the new values took effect July 1, 1959 (NIST; Federal Register, July 1, 1959).
Since a yard is 36 inches, 0.9144 m ÷ 36 = 0.0254 m, which is 2.54 cm per inch. The meter itself is defined from the speed of light, so the inch is now tied to a physical constant.
What about the U.S. survey foot?
Some old U.S. land surveys used the “U.S. survey foot,” which is slightly longer than the international foot; the 1959 Federal Register notice put the difference at 2 parts in one million. NIST says the survey foot has been superseded and should be avoided since January 1, 2023, except for historic and legacy applications (NIST, U.S. Survey Foot). For rulers, screens, clothing, height and everyday use, always use 2.54 cm per inch.
For other everyday unit changes, see our cooking conversion chart for cups, ounces and grams and our guide on how to calculate square footage, which also covers square inches.
Frequently asked questions
How many cm is 1 inch?
One inch is exactly 2.54 centimeters. The value has been an exact legal definition since July 1, 1959, so no rounding is involved.
How do you convert inches to cm?
Multiply the number of inches by 2.54. For example, 12 inches times 2.54 equals 30.48 cm.
How do you convert cm to inches?
Divide the number of centimeters by 2.54, or multiply by about 0.3937. For example, 30 cm divided by 2.54 is about 11.81 inches.
Is an inch exactly 2.54 cm?
Yes. NIST explains that the international inch is exactly 25.4 millimeters, which is exactly 2.54 centimeters, because the yard is defined as exactly 0.9144 meters.
How tall is 5 feet 7 inches in cm?
5 feet 7 inches is 67 inches. Multiply 67 by 2.54 to get 170.18 cm, or about 170 cm.
How many inches is 30 cm?
30 cm is about 11.81 inches, because 30 divided by 2.54 equals 11.811.
Sources
- NIST — SI Units: Length (metric redefinition of the inch)
- NIST — Guide to the SI, Appendix B.9: Factors for Units Listed by Kind of Quantity
- NIST — Ending the Era of the U.S. Survey Foot
- Federal Register, July 1, 1959 — Refinement of Values for the Yard and the Pound
Featured image: a measuring tape marked in inches and centimeters. Photo by Stilfehler, public domain, via Wikimedia Commons.