Inches to Millimeters formula
millimeters = inches × 25.4
Multiply the number of inches by 25.4 to get millimeters. To go the other way, multiply by 0.0393701 instead, or use the mm to inches converter.
Inches to Millimeters conversion table
Common inches to mm values, rounded for reading. The converter above keeps full precision.
| Inches | Millimeters |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 50 in | 1,270 mm |
| 75 in | 1,905 mm |
| 100 in | 2,540 mm |
| 250 in | 6,350 mm |
| 500 in | 12,700 mm |
| 1,000 in | 25,400 mm |
Worked example
To convert 10 in to millimeters, multiply by 25.4: the result is 254 mm. International inch, foot, yard and mile definitions are exact. One inch equals exactly 2.54 centimeters.
Frequently asked questions
How many millimeters are in a inch?
One inch equals 25.4 millimeters (1 in = 25.4 mm).
What is 10 inches in millimeters?
10 in converts to 254 mm. Enter any other value in the converter above to see it recalculated instantly.
How do I convert millimeters back to inches?
Reverse the calculation: one millimeter equals 0.0393701 inches. You can also swap the units in the converter or open the mm to inches page.
Related length conversions
Need a different pair? Open the full length converter to choose any two units.