Convert inches to millimeters
Enter a value in inches to convert it to millimeters.
inches to millimeters reference
| inches | millimeters |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 25 in | 635 mm |
| 50 in | 1270 mm |
| 100 in | 2540 mm |
The conversion factor
One inch is 25.4 millimeters. So to convert, multiply your figure in inches by 25.4. To go the other way, multiply millimeters by 0.03937008, or use the millimeters to inches converter.
Doing it in your head
For a quick estimate, round the factor: roughly "times 25". Use the exact converter above when the number matters.
Where this conversion comes up
Height, distance, DIY measurements, maps, and any spec sheet that mixes metric and imperial.
See the common unit conversions cheat sheet for the factors worth memorising.
Related tools
Frequently asked questions
How many millimeters are in a inch?
1 inch = 25.4 millimeters.
What is the formula to convert inches to millimeters?
Multiply the number of inches by 25.4. To go back the other way, multiply millimeters by 0.03937008.
What is 10 inches in millimeters?
10 inches = 254 millimeters. The reference table below lists more common values.
Is this converter accurate?
It uses the internationally defined conversion factors and computes at full floating-point precision, then rounds only the displayed result. For everyday purposes it is exact; for legal, engineering or scientific work, confirm the required number of significant figures.
Does it work offline?
Yes. The conversion runs in your browser with no server call, so it keeps working with no connection, and nothing you enter is uploaded.
Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.