Mm to Inches Converter
Enter a value in millimeters to convert it to inches — 1 mm = 0.0394 in.
Reviewed by the ToolNestr Editorial Team — July 2026
How to convert millimeters to inches
Converting millimeters to inches is a simple multiplication: take your length in millimeters and multiply by the fixed conversion factor of 0.0393700787 to get inches. Because the factor never changes, the same calculation works for any value, from tiny amounts to very large ones. The converter above applies it the moment you type, with no rounding errors in the underlying maths.
Engineers and makers use it for fine tolerances, fasteners and material thickness given in millimeters. Knowing how to move between millimeters and inches is useful whenever measurements are given in one system but you need them in the other — for shopping, travel, study, cooking, engineering or simply comparing figures from different countries.
The reference table below lists common millimeters values already converted to inches, so you can read off everyday amounts at a glance without typing. For the opposite direction, use the Inches to Mm Converter, which reverses the calculation exactly.
The formula and a worked example
Formula
in = mm × 0.0393700787
Worked example
To convert 10 millimeters: 10 × 0.0393700787 = 0.3937 in. To convert 25 millimeters: 25 × 0.0393700787 = 0.9843 in.
Mm to Inches conversion table
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.0394 |
| 2 | 0.0787 |
| 5 | 0.1969 |
| 10 | 0.3937 |
| 25 | 0.9843 |
| 50 | 1.9685 |
| 100 | 3.937 |
| 250 | 9.8425 |
| 500 | 19.685 |
| 1,000 | 39.3701 |
Values are rounded for display; the converter above keeps full precision.
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Frequently asked questions
How do I convert millimeters to inches?
Multiply the number of millimeters by 0.0393700787. For example, 10 mm × 0.0393700787 = 0.3937 in. The converter above does this automatically.
How many inches are in one millimeters?
There are 0.0394 inches in one millimeters. Multiply by 0.0393700787 for any amount.
Is this Mm to Inches converter accurate?
Yes. It uses the exact conversion factor of 0.0393700787, so results are precise. Values shown in the table are rounded for readability.
How do I convert inches back to millimeters?
Use our Inches to Mm Converter for the reverse direction, or divide the inches value by 0.0393700787.