Screw Gauges and Conversion
The diameters of some screws (especially woodscrews and self-tapping screws for metal) can be described with gauge numbers, rather than metric diameters. This guide shows you how to convert between the two.
The gauge of the screw is determined by the thread diameter, as pictured above. From this measurement, the table below will help you identify the correct screw gauge.
| Gauge | Metric diameter (mm) | Imperial diameter (inch) |
|---|---|---|
| 0g | 1.5 | 1/16 |
| 1g | 1.9 | 5/64 |
| 2g | 2.25 | 3/32 |
| 3g | 2.5 | 13/128 |
| 4g | 2.9 | 7/64 (No4) |
| 5g | 3.3 | 1/8 |
| 6g | 3.5 | 9/64 (No6) |
| 7g | 3.9 | 5/32 |
| 8g | 4.2 | 11/64 (No8) |
| 9g | 4.5 | 23/128 |
| 10g | 4.8 | 3/16 (No10) |
| 12g | 5.5 | 7/32 (No12) |
| 13g | 6.1 | 15/64 |
| 14g | 6.3 | 1/4 (No14) |
| 15g | 6.5 | 1/4 |
| 16g | 6.8 | 17/64 |
| 18g | 7.5 | 19/64 |
| 20g | 8.1 | 21/64 |
| 24g | 9.4 | 3/8 |