30 amp wire size
A 30 amp circuit needs 10 AWG copper wire with 75 °C terminations. Aluminum wire is not used for circuits this small.
30 amp wire size by termination rating
| Termination rating | Copper | Aluminum |
|---|---|---|
| 60 °C, NM-B | 10 AWG | copper only |
| 75 °C, THHN | 10 AWG | copper only |
| Ground wire | 10 AWG | — |
30 amp wire size by distance at 240 V
Sizes that keep the voltage drop within 3% on a 240 V circuit loaded to the full 30 A, 75 °C terminations. The copper ground wire grows with the hot wires on long runs.
| One-way distance | Copper | Drop | Copper ground |
|---|---|---|---|
| 25 ft | 10 AWG | 0.8% | 10 AWG |
| 50 ft | 10 AWG | 1.6% | 10 AWG |
| 100 ft | 8 AWG | 2.0% | 8 AWG |
| 150 ft | 8 AWG | 2.9% | 8 AWG |
| 200 ft | 6 AWG | 2.5% | 6 AWG |
| 300 ft | 4 AWG | 2.3% | 4 AWG |
Check your own 30 amp run
What are you sizing for?
A
ft
From the panel to the load, not there and back
Voltage
Conductor
Termination rating
Result
10 AWG copper
Ampacity sets the size; the voltage drop is within 3%.
- Breaker
- 30 A
- Voltage drop
- 3.7 V (1.6%)
- Volts at the load
- 236.3 V
- Ground wire
- 10 AWG copper
How it is calculated
- Breaker: 30 A rounded up to a standard size = 30 A.
- Smallest copper conductor rated for 30 A at 75 °C: 10 AWG.
- Drop = 2 × K × 30 A × 50 ft ÷ 10,380 cmil = 3.73 V, target 3% of 240 V.
What a 30 amp circuit is used for
- Electric dryer
- Electric water heater
- 30 amp RV outlet (120 V)