Wire size for 30 amps by distance (240 V, 3% drop)
| One-way distance | Copper | Drop | Aluminum |
|---|---|---|---|
| 25 ft | 10 AWG | 0.76% | 8 AWG |
| 50 ft | 10 AWG | 1.51% | 8 AWG |
| 75 ft | 10 AWG | 2.27% | 8 AWG |
| 100 ft | 8 AWG | 1.91% | 6 AWG |
| 150 ft | 8 AWG | 2.87% | 4 AWG |
| 200 ft | 6 AWG | 2.46% | 4 AWG |
| 250 ft | 4 AWG | 1.93% | 3 AWG |
| 300 ft | 4 AWG | 2.31% | 2 AWG |
Single-phase 240 V, 75°C terminals, non-continuous load. For continuous loads (3+ hours) size for 38 A.
Common 30 A circuits
30 amp circuits typically feed water heaters, dryers and small A/C units. The breaker protects the wire, so never pair a 30 A breaker with wire rated below 30 A.
Frequently asked questions
Can I use 10 AWG wire on a 30 amp breaker?
Yes. 10 AWG copper is rated at least 30 A even in the 60°C column, so it works for NM-B cable and THHN alike, as long as voltage drop is acceptable.
How far can I run 10 AWG wire at 30 amps?
At 240 V with a 3% voltage-drop limit, about 75 ft one way. Beyond that, go up one size.