How to use Millimeters to Inches
Enter the value in mm, then select Calculate. The result is shown in in. Returns decimal inches rather than a rounded fractional inch.
The formula
in = mm ÷ 25.4
Examples
- 1 millimeters to inches
0.03937008 in
- 10 millimeters to inches
0.39370079 in
- 250 millimeters to inches
9.84251969 in
Millimeters to Inches conversion table
| Millimeters | Inches |
|---|---|
| 1 | 0.0394 in |
| 2 | 0.0787 in |
| 3 | 0.1181 in |
| 4 | 0.1575 in |
| 5 | 0.1969 in |
| 6 | 0.2362 in |
| 7 | 0.2756 in |
| 8 | 0.315 in |
| 9 | 0.3543 in |
| 10 | 0.3937 in |
| 15 | 0.5906 in |
| 20 | 0.7874 in |
| 25 | 0.9843 in |
| 30 | 1.1811 in |
| 40 | 1.5748 in |
| 50 | 1.9685 in |
| 75 | 2.9528 in |
| 100 | 3.937 in |
| 250 | 9.8425 in |
| 500 | 19.685 in |
| 1,000 | 39.3701 in |
Limitations and assumptions
Uses standard unit definitions. Results are rounded to at most eight decimal places; very small results may round to zero. Returns decimal inches rather than a rounded fractional inch.
Frequently asked questions
How many inches are in one millimeter?
One millimeter equals 0.03937008 in. The formula is in = mm ÷ 25.4.
How do I convert millimeters to inches?
Use in = mm ÷ 25.4. For example, 10 millimeters gives 0.39370079 in. Enter your own value above and the converter does the arithmetic for you.
How do I convert inches back to millimeters?
Use the Inches to Millimeters converter, or invert the factor by dividing instead of multiplying.
Is this conversion exact?
Every length conversion here hangs on one exact definition, 1 inch = 2.54 cm, so results are exact apart from display rounding.
Reference source
Checked against the official reference on nist.gov.
Formula, example and source checked 2026-11-09. This is a content check, not independent expert certification.