Convert inches to millimeters
1 in = 25.4 mm. Change the amount below, or read the formula and the reference table further down.
1 inch equals
millimeters
1 in = 25.4 mm
The formula
Inches and millimeters both measure length from the same zero, so a single multiplier does the job.
mm = in × 25.4
Going the other way? Convert millimeters to inches.
Inches to millimeters table
Common values, rounded for reading.
| Inches (in) | Millimeters (mm) |
|---|---|
| 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 |
| 15 | 381 |
| 20 | 508 |
| 25 | 635 |
| 30 | 762 |
| 40 | 1,016 |
| 50 | 1,270 |
| 75 | 1,905 |
| 100 | 2,540 |
| 250 | 6,350 |
| 500 | 12,700 |
| 1,000 | 25,400 |
Questions people ask
- How many millimeters are in a inch?
- One inch equals 25.4 millimeters.
- How do I convert inches to millimeters by hand?
- Multiply the number of inches by 25.4. For a rough check, 25.4 is close enough for most everyday use.
- What is 1 inch in millimeters?
- 1 inch is 25.4 millimeters.
Calcuit generates this page from a unit table, so the factors here match every other page on the site.