Millimeters to Inches
25.4 millimeters = 1 international inch. Conversion runs in your browser.
Conversion result
Millimeters ÷ 25.4 = inches; inches × 25.4 = millimeters.
Primary source: NIST SP 811, Appendix B.8 conversion factors. One international inch is exactly 25.4 millimeters.
Worked example: 25.4 ÷ 25.4 = 1 inch; 50 millimeters = 1.96850393701 inches.
Common conversion values
| millimeters | international inches |
|---|---|
| 1 | 0.0393700787402 |
| 10 | 0.393700787402 |
| 25.4 | 1 |
| 50 | 1.96850393701 |
| 100 | 3.93700787402 |
The table shows reference quantities; displayed results are rounded to at most 12 significant digits. Reverse conversions divide by the forward factor.
How to use this tool
Enter a quantity in millimeters, select the forward or reverse direction, and choose Convert. Decimal, fraction and mixed-fraction inputs are supported.
Frequently asked questions
What factor is used?
One international inch is exactly 25.4 millimeters. Millimeters ÷ 25.4 = inches; inches × 25.4 = millimeters.
Can I convert in reverse?
Yes. Select the reverse direction; it uses the same exact unit definitions and reverses the factor.
What does this page calculate?
It converts between the named units. Ounces means avoirdupois mass ounces here, not fluid ounces. The result does not imply measurement accuracy.