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Millimeters to inches is one of the most useful conversions in DIY, woodworking, manufacturing, 3D printing and photography — anywhere you might be working between metric drawings and imperial tools. This calculator gives you the exact decimal inch equivalent for any millimeter value.
How to convert mm to inches
One inch is defined as exactly 25.4 millimeters, which means 1 mm equals 0.03937 inches. To convert any value in mm to inches, divide by 25.4 — or, equivalently, multiply by 0.03937.
Worked example: 50 mm in inches is calculated as 50 / 25.4 ≈ 1.969 inches.
Why convert mm to inches?
Most of the world specifies dimensions in millimeters, but the United States — and many older shop tools, fasteners and lumber sizes — still use inches. If you are reading a metric blueprint and using imperial tools, or buying parts from an international supplier, you will need to convert constantly. The conversion is exact, so there is no rounding error to worry about.
What is the mm to inches formula?
The formula for converting millimeters to inches is:
inches = mm / 25.4
How do I convert inches to mm?
To convert inches to millimeters, multiply by 25.4:
mm = inches × 25.4
Or use our inches to mm calculator.
Common fractional inch equivalents
If you need to read fractional inches from a ruler, here are the common ones in mm:
- 1/16" ≈ 1.59 mm
- 1/8" ≈ 3.18 mm
- 1/4" = 6.35 mm
- 3/8" ≈ 9.53 mm
- 1/2" = 12.7 mm
- 3/4" = 19.05 mm
- 1" = 25.4 mm
MM to Inches Conversion Table
This table shows common values in millimeters and their equivalent in inches.
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.039 |
| 5 | 0.197 |
| 10 | 0.394 |
| 15 | 0.591 |
| 20 | 0.787 |
| 25 | 0.984 |
| 30 | 1.181 |
| 40 | 1.575 |
| 50 | 1.969 |
| 75 | 2.953 |
| 100 | 3.937 |
| 150 | 5.906 |
| 200 | 7.874 |
| 500 | 19.685 |
| 1000 | 39.370 |