Convert millimeters to inches in one step. Type a value, see the answer and a few related units, and use the chart below for common values. Free, private, and runs entirely in your browser.
Divide the number of millimeters by 25.4 to get inches. The units are defined in terms of each other, so the conversion is exact. The calculator uses the full-precision factor, while the factor printed here is rounded.
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.0394 |
| 2 | 0.0787 |
| 3 | 0.1181 |
| 5 | 0.1969 |
| 6 | 0.2362 |
| 8 | 0.315 |
| 10 | 0.3937 |
| 12 | 0.4724 |
| 16 | 0.6299 |
| 20 | 0.7874 |
| 25.4 | 1 |
| 50 | 1.9685 |
How many mm is 1 inch? Exactly 25.4 mm.
What is 10 mm in inches? About 0.3937 inch, which is nearly 3/8 inch (0.375).
Convert 10 millimeters to inches: 10 ÷ 25.4 = 0.3937 in.
Is the millimeters to inches factor exact? Yes. The units are defined in terms of each other, so the factor has no uncertainty.
Can I convert inches back to millimeters? Yes. Use the converter in the opposite direction, which is linked below.
The millimeter, one thousandth of a meter, comes from the metric system established in France in the 1790s. Because the inch has been defined as exactly 25.4 millimeters since 1959, converting millimeters to inches means dividing by 25.4 with no rounding error in the definition.
Use this converter for drill bits, bolts, camera lenses, pipe and sheet thickness and jewelry sizes that are quoted in millimeters. A 10 mm socket is 0.3937 inch, close to 3/8 inch, which explains why sizes in the two systems are often paired.
What is a quick estimate for millimeters to inches? Multiply or divide by the rounded factor, 1 ÷ 25.4, then use the calculator for the exact value.
Does the converter work on a phone? Yes. It runs in your browser and updates when you press Calculate.