50 amp wire size
A 50 amp circuit needs 8 AWG copper or 6 AWG aluminum wire with 75 °C terminations. In NM-B cable (Romex), which is limited to the 60 °C column, a 50 amp circuit needs 6 AWG copper.
50 amp wire size by termination rating
| Termination rating | Copper | Aluminum |
|---|---|---|
| 60 °C, NM-B | 6 AWG | 4 AWG |
| 75 °C, THHN | 8 AWG | 6 AWG |
| Ground wire | 10 AWG | 8 AWG |
50 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 50 A, 75 °C terminations. The copper ground wire grows with the hot wires on long runs.
| One-way distance | Copper | Drop | Copper ground | Aluminum | Drop |
|---|---|---|---|---|---|
| 25 ft | 8 AWG | 0.8% | 10 AWG | 6 AWG | 0.8% |
| 50 ft | 8 AWG | 1.6% | 10 AWG | 6 AWG | 1.7% |
| 100 ft | 6 AWG | 2.0% | 8 AWG | 4 AWG | 2.1% |
| 150 ft | 4 AWG | 1.9% | 4 AWG | 3 AWG | 2.5% |
| 200 ft | 4 AWG | 2.6% | 4 AWG | 2 AWG | 2.7% |
| 300 ft | 2 AWG | 2.4% | 4 AWG | 1/0 AWG | 2.5% |
- Copper
- Aluminum
Check your own 50 amp run
What are you sizing for?
A
ft
From the panel to the load, not there and back
Voltage
Conductor
Termination rating
Result
8 AWG copper
Ampacity sets the size; the voltage drop is within 3%.
- Breaker
- 50 A
- Voltage drop
- 3.9 V (1.6%)
- Volts at the load
- 236.1 V
- Ground wire
- 10 AWG copper
How it is calculated
- Breaker: 50 A rounded up to a standard size = 50 A.
- Smallest copper conductor rated for 50 A at 75 °C: 8 AWG.
- Drop = 2 × K × 50 A × 50 ft ÷ 16,510 cmil = 3.91 V, target 3% of 240 V.
What a 50 amp circuit is used for
- Electric range
- Level 2 EV charger drawing 40 A
- 50 amp RV outlet
- Welder