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MM to Inches converter
Enter a number, fraction, power, π, or arithmetic expression.1 mm = 0.0393700787402 in inches = millimeters ÷ 25.4
Ready for local conversionMM to Inches formula
inches = millimeters ÷ 25.4
1 millimeter = 0.03937007874015748 inches
One international inch contains exactly 25.4 millimeters, so dividing by 25.4 is the standards-based conversion.
How to convert Millimeters to Inches
Divide millimeters by 25.4. If a drawing requires thousandths of an inch, keep at least four or five significant digits before applying its tolerance rules.
Example calculation
A 254 mm component is exactly 10 inches long: 254 ÷ 25.4 = 10.
254 mm = 10 in
When this conversion is useful
The conversion is especially helpful when pairing metric parts with inch-based drill bits, stock material, workshop tools, or technical documentation.
Common Millimeters to Inches conversions
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.0393700787402 |
| 10 | 0.393700787402 |
| 25.4 | 1 |
| 100 | 3.93700787402 |
| 254 | 10 |
| 1000 | 39.3700787402 |
MM to Inches FAQ
Yes. The international inch is defined as exactly 25.4 millimeters.
One millimeter is about 0.03937 inch, which lies between 1/32 inch and 3/64 inch. Decimal inches are usually clearer for this small value.
A tiny rounding difference can matter when tolerances stack across several parts. Preserve the source measurement's meaningful precision until the final specification.