1/0 AWG wire size
8.251 mm · 53.475 mm²
0.3249 in diameter · 0.322 Ω/km in copper · 125 A (NEC 60 °C copper)
What 1/0 AWG is used for
Feeders, welding leads and battery cable in vehicles.
The numbers
| Diameter | 8.251 mm · 0.3249 in |
| Cross-sectional area | 53.4751 mm² |
| Resistance, copper | 0.322 Ω/km · 0.098 Ω per 1,000 ft |
| Resistance, aluminium | 0.527 Ω/km |
| NEC 60 °C copper ampacity | 125 A |
How 1/0 compares
The gauge scale is geometric, so the useful comparisons are ratios rather than differences. 4/0 AWG has twice the copper of 1/0 — 107.219 mm² against 53.475 — and therefore half the resistance per metre. Going the other way, 3 AWG has half the area and twice the resistance.
| Gauge | Diameter | Area | Ω/km copper | vs 1/0 |
|---|---|---|---|---|
| 4/0 | 11.684 mm | 107.219 mm² | 0.16 | 2.01× the area |
| 3/0 | 10.405 mm | 85.029 mm² | 0.2 | 1.59× the area |
| 2/0 | 9.266 mm | 67.431 mm² | 0.26 | 1.26× the area |
| 1 | 7.348 mm | 42.408 mm² | 0.41 | 0.79× the area |
| 2 | 6.544 mm | 33.631 mm² | 0.51 | 0.63× the area |
| 3 | 5.827 mm | 26.67 mm² | 0.65 | 0.5× the area |
| 4 | 5.189 mm | 21.151 mm² | 0.82 | 0.4× the area |
| 6 | 4.115 mm | 13.302 mm² | 1.3 | 0.25× the area |
Frequently asked questions
What is 1/0 AWG in mm?
8.251 mm in diameter (0.3249 inches), with a cross-sectional area of 53.475 mm².
How many amps can 1/0 AWG copper carry?
125 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 1/0 AWG copper?
0.322 Ω per kilometre, or 0.098 Ω per 1,000 feet, for annealed copper at 20 °C. The same gauge in aluminium is about 0.53 Ω/km — 1.64 times higher, which is why aluminium wiring is sized larger for the same load.
How much thicker is 4/0 AWG than 1/0?
Three gauges lower is twice the cross-sectional area — 107.219 mm² against 53.475, a ratio of 2.005. That is not a coincidence: the AWG formula raises 92 to the power of (36−n)/39, and 92^(6/39) is 2.005.