The short answer
- 1 in = 25.4 mm
- 1 mm ≈ 0.03937008 in
Worked example0.5 in × 25.4 = 12.7 mm
UNIT CONVERSION
← Length converterInches to millimetres
To convert inches to millimetres, multiply the number of inches by 25.4.
What the units mean
Inch. The inch is exactly 2.54 centimetres, fixed by the international yard and pound agreement of 1959. There are 12 inches in a foot.
Millimetre. The millimetre is one thousandth of a metre.
Inches to millimetres table
| Inches (in) | Millimetres (mm) |
|---|---|
| 0.5 | 12.7 |
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 5 | 127 |
| 6 | 152.4 |
| 7 | 177.8 |
| 8 | 203.2 |
| 9 | 228.6 |
| 10 | 254 |
| 12 | 304.8 |
| 15 | 381 |
| 20 | 508 |
| 25 | 635 |
| 30 | 762 |
| 40 | 1,016 |
| 50 | 1,270 |
| 60 | 1,524 |
| 70 | 1,778 |
| 75 | 1,905 |
| 80 | 2,032 |
| 90 | 2,286 |
| 100 | 2,540 |
| 150 | 3,810 |
| 200 | 5,080 |
| 250 | 6,350 |
| 500 | 12,700 |
| 1,000 | 25,400 |
Values are rounded to 7 significant figures.
Common questions
How do I convert inches to millimetres?
Multiply the number of inches by 25.4. For example, 0.5 in × 25.4 = 12.7 mm.
How many millimetres are in one inch?
One inch is exactly 25.4 millimetres.
Is this conversion exact?
Yes. Both units have exact legal definitions, so the factor is exact. Values on this page are rounded to 7 significant figures.