Quick answer
One inch equals 25.4 millimeters exactly; the table converts sixteenth-inch increments without adding project-specific assumptions.
| Fractional inch | Decimal inch | Millimeters |
|---|---|---|
| 0 | 0.0000 | 0.000 mm |
| 1/16 | 0.0625 | 1.587 mm |
| 1/8 | 0.1250 | 3.175 mm |
| 3/16 | 0.1875 | 4.762 mm |
| 1/4 | 0.2500 | 6.350 mm |
| 5/16 | 0.3125 | 7.938 mm |
| 3/8 | 0.3750 | 9.525 mm |
| 7/16 | 0.4375 | 11.112 mm |
| 1/2 | 0.5000 | 12.700 mm |
| 9/16 | 0.5625 | 14.287 mm |
| 5/8 | 0.6250 | 15.875 mm |
| 11/16 | 0.6875 | 17.462 mm |
| 3/4 | 0.7500 | 19.050 mm |
| 13/16 | 0.8125 | 20.637 mm |
| 7/8 | 0.8750 | 22.225 mm |
| 15/16 | 0.9375 | 23.812 mm |
| 1 | 1.0000 | 25.400 mm |
How to use this chart
- Find the fraction shown on the tape or product label.
- Use the decimal value for tools that require decimal inches.
- Use the millimeter value when reconciling Metric documentation.
Data basis
Mathematically generated from the exact definition 1 inch = 25.4 millimeters.