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Inches to millimeters is the precision conversion you reach for in DIY, woodworking, machining, 3D printing, and any project that mixes imperial and metric components. The conversion is exact — no rounding required. Enter the length in inches and the calculator returns the exact millimeter equivalent.
How to convert inches to mm
One inch is defined as exactly 25.4 millimeters. To convert any length in inches to mm, multiply by 25.4.
Worked example: 2 inches in mm is calculated as 2 × 25.4 = 50.8 mm.
Why mm and inches?
Most of the world specifies dimensions in millimeters because it offers very fine resolution (1 mm increments) without resorting to fractions. The United States and a few other countries continue to use inches for many trades and consumer goods. Because the international inch is defined as exactly 25.4 mm, converting between the two is precise and lossless.
What is the inches to mm formula?
The formula for converting inches to millimeters is:
mm = inches × 25.4
How do I convert mm to inches?
To convert millimeters to inches, divide by 25.4:
inches = mm / 25.4
Or use our mm to inches calculator.
Common fractional inch values in mm
- 1/16" = 1.5875 mm
- 1/8" = 3.175 mm
- 1/4" = 6.35 mm
- 3/8" = 9.525 mm
- 1/2" = 12.7 mm
- 5/8" = 15.875 mm
- 3/4" = 19.05 mm
- 7/8" = 22.225 mm
- 1" = 25.4 mm
Inches to MM Conversion Table
This table shows common values in inches and their equivalent in millimeters.
| Inches (in) | Millimeters (mm) |
|---|---|
| 0.5 | 12.7 |
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 5 | 127.0 |
| 6 | 152.4 |
| 8 | 203.2 |
| 10 | 254.0 |
| 12 | 304.8 |
| 15 | 381.0 |
| 20 | 508.0 |
| 24 | 609.6 |
| 36 | 914.4 |
| 48 | 1219.2 |