What size wire for a 50 amp circuit?
People search “50 amp wire size” looking for one gauge. The useful answer is which check limited it.
How to run this check
- Enter 240 V, 50 A, copper, and one-way feet.
- If the cable is NM-B, switch the column to 60 °C and run it again.
- Read whether ampacity or voltage drop picked the size.
Why 8 AWG and 6 AWG both show up online
8 AWG copper is 50 A at the 75 °C planning column and 40 A at 60 °C. 6 AWG copper is 65 A at 75 °C and 55 A at 60 °C.
A conduit THHN job with 75 °C terminations can start smaller than an NM-B job that is stuck on the 60 °C column. That fork is why a one-line “always 6 AWG” answer is sloppy.
Length can erase the 8 AWG answer
At 150 ft one-way, 50 A, 240 V, 75 °C, the recommended size is 4 AWG and the limit is voltage drop.
If you only looked up ampacity, you would still think 8 AWG was fine. That is the whole point of running both checks on one page.
Planning walk-through for 50 A, 240 V, copper, 3% target
| Column and length | Recommended size | What limited it | Voltage drop |
|---|---|---|---|
| 75 °C, 40 ft | 8 AWG | Ampacity | 3.1 V / 1.3% |
| 60 °C, 40 ft | 6 AWG | Ampacity | 2.0 V / 0.8% |
| 75 °C, 150 ft | 4 AWG | Voltage drop | 4.6 V / 1.9% |
Related
FAQ
Is 6 AWG copper required for every 50 A circuit?
No. It is a common conservative pick, especially on 60 °C NM. A short 75 °C THHN run can plan at 8 AWG after you verify terminations.
Does this include EV charger continuous-load rules?
No. Continuous-load 125% is not applied automatically. Enter the current you are actually sizing to.
Planning reference only. Verify against the current NEC, manufacturer data, and the authority having jurisdiction. This is not engineering advice or a license substitute.