Convert inches to millimeters
Inch (in) to millimeter (mm). One inch equals 25.4 millimeters.
Formula
Inch to millimeter conversion table
| Inches | Millimeters | Millimeters | Inches |
|---|---|---|---|
| 1 in | 25.4 mm | 1 mm | 0.03937 in |
| 2 in | 50.8 mm | 2 mm | 0.07874 in |
| 3 in | 76.2 mm | 3 mm | 0.11811 in |
| 5 in | 127 mm | 5 mm | 0.19685 in |
| 10 in | 254 mm | 10 mm | 0.393701 in |
| 20 in | 508 mm | 20 mm | 0.787402 in |
| 50 in | 1270 mm | 50 mm | 1.9685 in |
| 100 in | 2540 mm | 100 mm | 3.937 in |
| 500 in | 12700 mm | 500 mm | 19.685 in |
| 1000 in | 25400 mm | 1000 mm | 39.3701 in |
To convert inches to millimeters, multiply the number of inches by 25.4. One inch equals 25.4 millimeters, and one millimeter equals 0.03937 inches, so the relationship is fixed and exact. As a worked example, 10 in comes to 254 mm. Enter your own figure in the converter above to get an instant answer, or use the swap button to flip the direction. This is a length conversion, and like every tool on UnitGlide it runs locally in your browser with no account or upload required. The table further down shows a range of common inch values already worked out in millimeters, plus the reverse millimeter to inch direction, which is handy for quick reference or double-checking a result by hand.
Frequently asked questions
How many millimeters are in an inch?
One inch equals 25.4 millimeters. The ratio is constant, so you can multiply any number of inches by 25.4 to get millimeters.
What is the formula to convert inches to millimeters?
Use millimeters = inches × 25.4. UnitGlide applies this exact formula for every value, so results stay accurate across the whole range.
How do I convert millimeters back to inches?
Go the other way by using one millimeter equals 0.03937 inches. You can also press the swap button in the converter above to flip the direction in one click.
Is this inch to millimeter converter accurate?
Yes. It uses internationally defined SI conversion factors, as maintained by the BIPM, and all math runs in your browser so nothing is rounded away on a server. For everyday use the displayed precision is more than enough.