SWG and AWG side by side
Both systems give thinner wire a bigger number, but the steps are different. SWG sizes are set in round thousandths of an inch (mils); for example, 20 SWG is 36 mils, or 0.036 inch.
| Gauge | SWG | AWG |
|---|---|---|
| 14 | 2.03 mm | 1.63 mm |
| 16 | 1.63 mm | 1.29 mm |
| 18 | 1.22 mm | 1.02 mm |
| 20 | 0.91 mm | 0.81 mm |
| 22 | 0.71 mm | 0.64 mm |
| 24 | 0.56 mm | 0.51 mm |
At these sizes, an SWG number is one or two AWG numbers thicker: 16 SWG (1.63 mm) matches 14 AWG, and 20 SWG (0.91 mm) matches 19 AWG.
When you’ll see it
You may meet SWG on British patterns and wire. If a pattern says “20 gauge” without saying which system, compare the millimetre size instead. See wire gauge (AWG) for the American scale.