inch to millimetre — free converter
Formula
millimetre = inch × 25.4
Worked example
15 inches = 381 millimetres.
Conversion table
| Inch | Millimetre |
|---|---|
| 1 inches | 25.4 millimetres |
| 2 inches | 50.8 millimetres |
| 5 inches | 127 millimetres |
| 10 inches | 254 millimetres |
| 25 inches | 635 millimetres |
| 50 inches | 1,270 millimetres |
| 100 inches | 2,540 millimetres |
What these units mean
An inch is the imperial step used on rulers in the United States and for screen sizes. A millimetre is a tiny metric step, useful for small measurements like a screw or a pencil line. When you change from inches to millimetres, you are simply expressing the same amount on a different scale, so the quantity itself does not change — only the number and the unit label do. A quick everyday check helps: picture the amount in your own life first, then let the converter do the arithmetic, and the result should feel roughly right before you use it for a purchase, a recipe or a journey.
FAQs about inch to millimetre
How many millimetres are in 1 inch?
1 inch = 25.4 millimetre.
What is the formula for inch to millimetre?
millimetre = inch × 25.4. This conversion is a multiplication by a fixed standard factor.
What is 15 inches in millimetres?
15 inches = 381 millimetres.
How do I convert millimetres back to inches?
Use the reverse page: millimetre to inch. The converter on that page swaps the direction for you.
Is the inch to millimetre result exact?
The factor is the standard published factor, and the converter shows the result rounded for reading. For everyday use this is exact enough; for engineering or laboratory work, check the rounding your task requires.