Inches to Millimeters Converter
Convert inches to millimeters instantly. 1 in = 25.4 mm. Free two-way converter with the formula and a quick reference table.
How to convert inches to millimeters
millimeters = inches × 25.4
One inch equals 25.4 millimeters, so to convert inches to millimeters you multiply by 25.4. Going the other way, one millimeter is 0.03937 inches. Both units measure length, so the conversion is an exact ratio that never changes.
10 inches = 254 millimeters. Multiply your inch figure by the factor above (or just type it into the box) to convert any amount.
Need the other direction? millimeters to inches
inches to millimeters table
| inches (in) | millimeters (mm) |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 5 | 127 |
| 10 | 254 |
| 20 | 508 |
| 25 | 635 |
| 50 | 1,270 |
| 100 | 2,540 |
| 250 | 6,350 |
| 500 | 12,700 |
| 1,000 | 25,400 |
Frequently asked questions
How many millimeters are in a inch?
One inch equals 25.4 millimeters. So to convert, multiply the number of inches by 25.4.
How do I convert inches to millimeters?
Multiply by 25.4, or simply enter the value in the converter above — it does the math instantly and works both ways.
Is this conversion exact?
Yes — both units measure the same quantity, so the ratio is fixed and this uses the standard internationally-agreed factor.