How to convert inches to millimeters
Inches and Millimeters both measure length, so converting is a single multiplication. One in equals 25.4 mm, so you multiply your inches value by 25.4.
Formula: millimeters = inches × 25.4. For example, 10 in = 254 mm.
Inches to Millimeters conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635 |
| 50 | 1,270 |
| 100 | 2,540 |
| 1,000 | 25,400 |
Inches and Millimeters explained
Inches (in): An imperial unit equal to exactly 2.54 cm, used for screens, print and DIY.
Millimeters (mm): One-thousandth of a metre, used for small, precise measurements like rainfall or engineering tolerances.
When you'd convert inches to millimeters
You'll convert inches to millimeters whenever a measurement is given in one unit but you need it in the other — comparing inches and millimeters figures across regions, following a recipe or spec, or double-checking a number. Because 1 in is exactly 25.4 mm, the result is precise every time.
Frequently asked questions
How many millimeters are in a inche?
One in equals 25.4 mm. Multiply your inches figure by 25.4 to get millimeters.
What is the formula to convert inches to millimeters?
millimeters = inches × 25.4. The factor 25.4 is exact.
What is 2 inches in millimeters?
2 in = 50.8 mm. You can enter any value in the converter above to get an instant result.
Is this Inches to Millimeters converter accurate?
Yes. It uses the standard conversion factor (1 in = 25.4 mm) defined by BIPM — SI Brochure (definition of the metre), so results are exact to several decimal places.