Converters Inches to centimetres
Convert inches to centimetres with the exact factor of 2.54, plus screen sizes, paper sizes and a full reference chart.
1 in = 2.54 cm
centimetres = inches × 2.54
inches to centimetres
| in | cm |
|---|---|
| 1 | 2.54 |
| 2 | 5.08 |
| 3 | 7.62 |
| 4 | 10.16 |
| 5 | 12.7 |
| 10 | 25.4 |
| 15 | 38.1 |
| 20 | 50.8 |
| 25 | 63.5 |
| 50 | 127 |
| 75 | 190.5 |
| 100 | 254 |
| 500 | 1,270 |
| 1,000 | 2,540 |
One inch is exactly 2.54 centimetres.
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Cite this page
Reembun. (2026, July 28). Inches to centimetres. https://reembun.com/convert/length/inches-to-cm
How to use it
Type the inches
Decimals are fine. The centimetre figure updates as you type.
Go the other way
Swap units turns it into a centimetres to inches converter.
Copy it or read the table
The conversion is exact rather than approximate, because an inch is defined as 2.54 centimetres.
The formula
centimetres = inches × 2.54
inches = centimetres ÷ 2.54Exact by definition since 1959, when the United States, United Kingdom, Canada, Australia, New Zealand and South Africa agreed a common yard of exactly 0.9144 metres.
Quick reference
| Inches | cm | Inches | cm |
|---|---|---|---|
| 1 | 2.54 | 12 | 30.48 |
| 2 | 5.08 | 15 | 38.10 |
| 3 | 7.62 | 20 | 50.80 |
| 4 | 10.16 | 24 | 60.96 |
| 6 | 15.24 | 30 | 76.20 |
| 8 | 20.32 | 36 | 91.44 |
| 10 | 25.40 | 48 | 121.92 |
Note that 36 inches is exactly 91.44 cm, a yard, and the number the whole system is defined from.
Screen sizes
Screens are measured diagonally, in inches, worldwide.
| Diagonal | cm | Typically |
|---|---|---|
| 6.1” | 15.5 | Phone |
| 11” | 27.9 | Small tablet |
| 13.3” | 33.8 | Laptop |
| 15.6” | 39.6 | Laptop |
| 24” | 61.0 | Desktop monitor |
| 27” | 68.6 | Desktop monitor |
| 55” | 139.7 | Television |
| 65” | 165.1 | Television |
The diagonal alone does not tell you the width. That depends on aspect ratio. A 27-inch 16:9 monitor is 59.8 cm wide; a 27-inch 21:9 ultrawide is considerably wider and shorter.
Paper sizes
| Format | Inches | mm |
|---|---|---|
| US Letter | 8.5 × 11 | 216 × 279 |
| US Legal | 8.5 × 14 | 216 × 356 |
| A4 | 8.27 × 11.69 | 210 × 297 |
| A3 | 11.69 × 16.54 | 297 × 420 |
A4 and US Letter are close enough to look interchangeable and different enough to break a print layout. A4 is 6 mm narrower and 18 mm taller, which is why a document laid out for one prints with clipped margins on the other.
Mental arithmetic
Inches to cm: multiply by 2.5, then add 1.5%. For 8 inches: 20 plus 0.3 gives 20.3 cm. (True: 20.32)
cm to inches: divide by 2.5, then subtract 1.5%. For 50 cm: 20 minus 0.3 gives 19.7 inches. (True: 19.69)
Useful anchors: 30 cm is almost exactly a foot (11.81 inches), and 2.5 cm is almost exactly an inch.
Common questions
What is the exact factor?
One inch is exactly 2.54 centimetres. It is a definition rather than a measurement, fixed by the International Yard and Pound Agreement of 1959, before which the US and imperial inches differed slightly, enough to matter in precision engineering.
How do I convert in my head?
Multiply by 2.5 and add about 1.5%. For 10 inches, 25 plus 0.4 gives 25.4 cm, which happens to be exact. For rough work, treating an inch as 2.5 cm is within 2%.
Why are screens measured in inches everywhere?
Convention, and the fact that the diagonal measurement started with US television manufacturing and stuck globally. A 27-inch monitor is 68.58 cm diagonally in every country, including fully metric ones.
Is a US inch the same as a UK inch?
Now, yes. Both are exactly 2.54 cm since 1959. Before that the US inch was defined as 1/39.37 of a metre and the imperial inch slightly differently, giving a discrepancy of about two parts per million.
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