3/0 AWG wire size
10.405 mm · 85.029 mm²
0.4096 in diameter · 0.203 Ω/km in copper · 165 A (NEC 60 °C copper)
What 3/0 AWG is used for
Service entrance and large subpanel feeders.
The numbers
| Diameter | 10.405 mm · 0.4096 in |
| Cross-sectional area | 85.0288 mm² |
| Resistance, copper | 0.203 Ω/km · 0.062 Ω per 1,000 ft |
| Resistance, aluminium | 0.332 Ω/km |
| NEC 60 °C copper ampacity | 165 A |
How 3/0 compares
The gauge scale is geometric, so the useful comparisons are ratios rather than differences. Going the other way, 1 AWG has half the area and twice the resistance.
| Gauge | Diameter | Area | Ω/km copper | vs 3/0 |
|---|---|---|---|---|
| 4/0 | 11.684 mm | 107.219 mm² | 0.16 | 1.26× the area |
| 2/0 | 9.266 mm | 67.431 mm² | 0.26 | 0.79× the area |
| 1/0 | 8.251 mm | 53.475 mm² | 0.32 | 0.63× the area |
| 1 | 7.348 mm | 42.408 mm² | 0.41 | 0.5× the area |
| 2 | 6.544 mm | 33.631 mm² | 0.51 | 0.4× the area |
| 3 | 5.827 mm | 26.67 mm² | 0.65 | 0.31× the area |
| 4 | 5.189 mm | 21.151 mm² | 0.82 | 0.25× the area |
Frequently asked questions
What is 3/0 AWG in mm?
10.405 mm in diameter (0.4096 inches), with a cross-sectional area of 85.029 mm².
How many amps can 3/0 AWG copper carry?
165 A under the NEC 60 °C copper column, which is the figure that sets the breaker on an ordinary branch circuit. This is a starting point and not a permission: the real limit depends on insulation rating, ambient temperature, how many conductors share the run, and your local code.
What is the resistance of 3/0 AWG copper?
0.203 Ω per kilometre, or 0.062 Ω per 1,000 feet, for annealed copper at 20 °C. The same gauge in aluminium is about 0.33 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.