One inch is exactly 2.54 centimeters. Type a length in the calculator above and you get it in centimeters, millimeters, meters, feet, yards and miles at the same time; pick a different unit in the list to go the other way.
Inches to centimeters
| Inches | Centimeters |
|---|---|
| 1 | 2.54 |
| 2 | 5.08 |
| 3 | 7.62 |
| 4 | 10.16 |
| 6 | 15.24 |
| 8 | 20.32 |
| 10 | 25.40 |
| 12 (1 foot) | 30.48 |
| 18 | 45.72 |
| 24 | 60.96 |
| 36 (1 yard) | 91.44 |
Fractions of an inch in millimeters
Tape measures, drill bits and wrenches in the US are marked in fractions of an inch. Multiply the fraction by 25.4 to get millimeters:
| Fraction | Millimeters |
|---|---|
| 1/16 in | 1.59 mm |
| 1/8 in | 3.18 mm |
| 3/16 in | 4.76 mm |
| 1/4 in | 6.35 mm |
| 5/16 in | 7.94 mm |
| 3/8 in | 9.53 mm |
| 1/2 in | 12.70 mm |
| 5/8 in | 15.88 mm |
| 3/4 in | 19.05 mm |
| 7/8 in | 22.23 mm |
A 3/8-inch bolt is therefore close to, but not the same as, a 10 mm one: the difference of half a millimeter is enough for a wrench to slip.
Screen sizes in centimeters
TVs and monitors are sold by their diagonal in inches everywhere in the world, even where everything else is metric. For a 16:9 screen, the width is 87.2% of the diagonal and the height 49.0%:
| Screen | Diagonal | Width | Height |
|---|---|---|---|
| 24″ | 61.0 cm | 53.1 cm | 29.9 cm |
| 32″ | 81.3 cm | 70.8 cm | 39.8 cm |
| 43″ | 109.2 cm | 95.2 cm | 53.5 cm |
| 50″ | 127.0 cm | 110.7 cm | 62.3 cm |
| 55″ | 139.7 cm | 121.8 cm | 68.5 cm |
| 65″ | 165.1 cm | 143.9 cm | 80.9 cm |
| 75″ | 190.5 cm | 166.0 cm | 93.4 cm |
| 85″ | 215.9 cm | 188.2 cm | 105.8 cm |
These are the sizes of the picture itself. The frame usually adds 1–3 cm on each side, so measure the gap in your cabinet against the product sheet, not against this table.
Why exactly 2.54?
Until 1959 the American and British inches were slightly different. That year, the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa agreed on the international yard of 0.9144 m, which makes the inch (1/36 of a yard) exactly 25.4 mm. Every conversion on this page uses that definition, so the results are exact, not rounded estimates.
Quick tips
- Centimeters to inches in your head: multiply by 4, then divide by 10. 50 cm ≈ 20 in (exactly 19.69).
- Inches to centimeters in your head: multiply by 2.5, then add a little. 10 in ≈ 25 cm (exactly 25.4).
- Clothing sizes such as a 32-inch waist are 81.3 cm; a 34-inch inside leg is 86.4 cm.
The converter keeps working with no internet once you have opened it, which is handy in a hardware store with poor reception.
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54. Since 1959 the inch has been defined as 25.4 millimeters, so the conversion never needs rounding.
How do I convert centimeters to inches?
Divide by 2.54. For example, 30 cm ÷ 2.54 = 11.81 inches. To estimate in your head, multiply the centimeters by 4 and divide by 10: 30 × 0.4 = 12.
How big is a 55-inch TV in centimeters?
The 55 inches is the diagonal: 139.7 cm. A 16:9 screen of that size is about 121.8 cm wide and 68.5 cm tall, without the frame.
What is 5/8 of an inch in millimeters?
15.875 mm. Multiply the fraction by 25.4: 5 ÷ 8 × 25.4 = 15.875.
Sources
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