US and metric measurements
Millimeters to Inches Converter
Convert millimeters to decimal inches and an approximate inch fraction. Swap the units to enter decimal or fractional inches.
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Millimeters to decimal inches
Divide millimeters by 25.4: inches = millimeters ÷ 25.4. One international inch is exactly 25.4 millimeters.
Example: 10 mm
10 ÷ 25.4 ≈ 0.393701 in. Rounded to the nearest 1/16 inch, that is approximately 3/8 in. The rounded fraction corresponds to 9.525 mm, so it is not an exact equivalent of 10 mm.
Inches to millimeters
Swap the units and multiply inches by 25.4. For example, 1/2 in = 12.7 mm. You can enter a decimal or a fraction when inches is the input unit.
Use decimal results for precise dimensions
The fraction is a convenient rounded reading. For a part, drill size or fit with a tolerance, keep the decimal result and check the required dimensions. An approximate fraction does not identify an interchangeable component.
Millimeters to inches conversion table
| mm | in |
|---|---|
| 1 | 0.03937 |
| 5 | 0.19685 |
| 10 | 0.393701 |
| 12.7 | 0.5 |
| 25.4 | 1 |
| 50 | 1.968504 |
Conversion factors use international inches, feet, yards and miles. Display rounding does not change the underlying calculation. Use a period for decimal inputs; fractional inch results are approximate.