12 inches to cm — 30.48 centimetres
12 inches are exactly 30.48 centimetres. That is 304.8 millimetres or 0.3048 metres. Multiply by 2.54 to convert any value from inches to cm.
Inches to cm
LiveThe formula
Take the number of inches and multiply it by 2.54: 12 × 2.54 = 30.48 cm. The factor comes from the international definition of the units, so the result is exact rather than an estimate — only the displayed value is rounded.
| Result | 30.48 cm |
|---|---|
| In millimetres | 304.8 mm |
| In metres | 0.3048 m |
| In feet | 1 ft |
Where this measurement turns up
- Laptop screens
- tablets
- cake tins
- bike wheels
Worth knowing
The inch has been defined as exactly 2.54 centimetres since the international yard and pound agreement of 1959. Before that, the American inch and the British inch differed by a fraction of a micron — enough to matter in precision engineering, which is precisely why the standard was fixed.
The mistake to avoid
The usual slip is rounding the factor to 2.5 instead of 2.54. Over a small value the gap is invisible, but at 40 inches the difference between 100 cm and the correct 101.6 cm is enough to misjudge whether furniture clears a doorway.
Inches to cm — reference table
Neighbouring values, each with its own page.
Questions people ask
12 inches are exactly 30.48 centimetres. The calculation is 12 × 2.54.
Multiply the value in inches by 2.54. To go the other way, divide the cm figure by the same number.
The conversion factor is defined by international standard, so the underlying result is exact. We round the display to a sensible number of decimal places, which is why you may see a slightly shorter figure than a calculator gives.
For a rough estimate, multiply by 2.5 — close enough for everyday use. For anything that needs to be right, such as a form, a cut list or a shipping label, multiply by exactly 2.54 instead, since the shortcut drifts further from the true value as the number grows.
Need the reasoning, not just the number?
Our guides explain how each measurement is defined, where it is used and which mistakes cost people money.