Wire size for a 50 amp breaker
| Wire | Condition | Minimum size for 50 A |
|---|---|---|
| Copper | NM-B (Romex) cable or 60°C terminals | 6 AWG |
| Copper | THHN/THWN in conduit, 75°C terminals | 8 AWG |
| Aluminum | 75°C terminals | 6 AWG |
| Aluminum | 60°C terminals | 4 AWG |
8 AWG copper is rated 40 A in the 60°C column, 50 A at 75°C and 55 A at 90°C. The size above is the smallest whose ampacity is at least 50 A. Most modern breakers and panels have 75°C terminals, but a 50 A circuit is presumed 60°C unless the equipment is marked otherwise (NEC 110.14(C)).
Voltage drop: how far can 8 AWG run at 50 A?
The 8 AWG above carries 50 A safely but loses voltage over distance. At the full 50 A and 240 V, 8 AWG copper stays within the NEC's 3% recommendation for about 92 ft one way. 6 AWG stretches that to 146 ft.
| One-way distance | 8 AWG copper | 6 AWG copper | 4 AWG copper |
|---|---|---|---|
| 25 ft | 0.8% | 0.5% | 0.3% |
| 50 ft | 1.6% | 1.0% | 0.6% |
| 100 ft | 3.3% | 2.0% | 1.3% |
| 150 ft | 4.9% | 3.1% | 1.9% |
| 200 ft | 6.5% | 4.1% | 2.6% |
Percent drop at 50 A and 240 V.
On 120 V circuits, the 50 A percentages are twice these values.
Check your own 50 A run with the voltage drop calculator, or let the wire size calculator choose the size for you.
What a 50 amp circuit is used for
- Electric ranges and ovens (most are 50 A)
- Level 2 EV chargers drawing 40 A continuous
- Hot tubs and spas on smaller GFCI circuits
- RV pedestals rated 50 A and welders
Cable type matters
For NM-B (Romex), 8 AWG tops out at 40 A in the 60°C column, so a 50 A circuit uses 6/3 NM-B, which carries 55 A. Individual THHN conductors in conduit use the 75°C column, where 8 AWG is rated 50 A.
Continuous loads and common mistakes
On a 50 A breaker, a continuous load running three hours or more should not exceed 80% of the rating. That is 40 A, or about 9,600 W at 240 V. Many ranges list 50 A on the breaker but need far less in practice. The wire is still sized to the breaker.
For a 50 A breaker the ground wire comes from NEC Table 250.122. Use the ground wire size calculator. For other breaker sizes, see the breaker to wire size chart, or jump to 20 amps, 30 amps, 40 amps, 60 amps, 100 amps.
Frequently asked questions
What size wire for a 50 amp breaker?
8 AWG copper at 75°C terminals, or 6 AWG for NM-B cable. In aluminum use 6 AWG.
How far can 8 AWG wire run on 50 amps?
About 92 feet one way at 240 V before the voltage drop passes the NEC's 3% recommendation. Past that distance, step up to 6 AWG.
What size wire for a 50 amp range?
6/3 NM-B (Romex) cable, or 8 AWG THHN in conduit. Both fit a 50 A breaker.
What size wire for a 40 amp EV charger?
A 50 A breaker with 8 AWG THHN in conduit or 6 AWG NM-B cable, since the continuous load is sized at 125% (40 × 1.25 = 50 A).