20 AWG wire size
0.812 mm · 0.518 mm²
0.032 in diameter · 33.306 Ω/km in copper
What 20 AWG is used for
Signal wiring, small transformers and hobby electronics.
The numbers
| Diameter | 0.812 mm · 0.032 in |
| Cross-sectional area | 0.5176 mm² |
| Resistance, copper | 33.306 Ω/km · 10.152 Ω per 1,000 ft |
| Resistance, aluminium | 54.48 Ω/km |
| NEC 60 °C copper ampacity | — outside the common building-wire range |
How 20 compares
The gauge scale is geometric, so the useful comparisons are ratios rather than differences. 14 AWG is twice the diameter, which is four times the area.
| Gauge | Diameter | Area | Ω/km copper | vs 20 |
|---|---|---|---|---|
| 14 | 1.628 mm | 2.081 mm² | 8.28 | 4.02× the area |
| 16 | 1.291 mm | 1.309 mm² | 13.17 | 2.53× the area |
| 18 | 1.024 mm | 0.823 mm² | 20.95 | 1.59× the area |
| 22 | 0.644 mm | 0.326 mm² | 52.96 | 0.63× the area |
| 24 | 0.511 mm | 0.205 mm² | 84.21 | 0.4× the area |
| 26 | 0.405 mm | 0.129 mm² | 133.9 | 0.25× the area |
Frequently asked questions
What is 20 AWG in mm?
0.812 mm in diameter (0.032 inches), with a cross-sectional area of 0.518 mm².
Is 20 AWG used for power wiring?
Not for building circuits. It is a signal and low-current gauge — thinner than anything a domestic branch circuit uses.
What is the resistance of 20 AWG copper?
33.306 Ω per kilometre, or 10.152 Ω per 1,000 feet, for annealed copper at 20 °C. The same gauge in aluminium is about 54.48 Ω/km — 1.64 times higher, which is why aluminium wiring is sized larger for the same load.
Why do smaller AWG numbers mean thicker wire?
The number counts drawing operations. Wire is pulled through progressively smaller dies, and the gauge records how many passes it took — so more passes means a higher number and a thinner wire.