Convert Inches to Millimeters
Inches (in) to Millimeters (mm) — the formula, a worked example and a live converter, all in your browser.
Inches to Millimeters formula
To convert a measurement, multiply it by the fixed factor below:
mm = in × 25.4
Worked example
1 in = 1 × 25.4 = 25.4 mm.
Inches to Millimeters conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 1 | 25.4 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635 |
| 50 | 1270 |
| 100 | 2540 |
Common uses
Handy for machining, drilling and DIY when a part is specified in inches but your tools and drawings are in millimetres.
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Frequently asked questions
What is the formula to convert inches to millimeters?
Multiply the number of inches by 25.4 to get millimeters (mm = in × 25.4).
How many millimeters are in a inche?
One inche equals 25.4 millimeters.
Is this converter accurate?
Yes. It uses the exact internationally-defined conversion factors and runs entirely in your browser, so results match standards tables and nothing you type is uploaded.