How to convert Inches to Millimeters
The conversion is a single multiplication: 1 in = 25.4 mm. To convert inches to millimeters, multiply by 25.4. To go back, multiply millimeters by 0.03937 (or divide by 25.4). These factors are exact by definition.
Examples
- 1 in = 25.4 mm
- 12 in = 304.8 mm
Inches to Millimeters conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 5 | 127 |
| 10 | 254 |
| 20 | 508 |
| 25 | 635 |
| 50 | 1270 |
| 100 | 2540 |
Frequently asked questions
- How do I convert Millimeters back to Inches?
- Use the Millimeters to Inches converter, or just swap the units on the full unit converter — it shows every unit in the category at once.
- Are these conversion factors exact?
- Yes. The English units have been defined in metric terms since 1959, so the factors used here are exact by definition, not rounded approximations. Displayed results are rounded only for readability.
- Can I convert other units too?
- The unit converter also handles length, weight, volume, temperature, area, speed, pressure, energy, power, torque, and fuel economy — each with every unit shown side by side.