What Size Wire for 50 Amp?

The minimum gauge for a 50 amp breaker by cable type, and how distance changes it.

For a 50 amp circuit use 6 AWG copper NM-B cable (rated 55 A at 60 °C) or 8 AWG copper THHN in conduit when every terminal is rated 75 °C. In aluminum, 4 AWG at 60 °C or 6 AWG at 75 °C. At 240 V go one size up past 92 ft on 8 AWG or 146 ft on 6 AWG.

50 amp wire size by cable type

The difference between 6 and 8 AWG comes down to the weakest temperature rating in the circuit. Cable assemblies like NM-B are held to 60 °C no matter what the individual conductors inside are rated, which is why 6/3 NM-B is the cable sold for 50 A range circuits.

50 amp wire size by distance

Minimum size on a 240 V single-phase circuit carrying the full 50 A, with voltage drop held to 3%. Use this for subpanels, shops and pedestal runs where length is the deciding factor.

Ampacity: table value at the cable's temperature column ≥ 50 A (≥ 1.25 × load for a continuous load)
Max run = 0.03 × V × 1000 ÷ (2 × I × R)

The distance column is the second line solved for length: R is ohms per 1000 ft from NEC Chapter 9 Table 8 at 75 °C, and the 2 counts the trip out and back. For 6 AWG copper (R = 0.491) at 50 A and 240 V: 7200 ÷ (100 × 0.491) = 146 ft. The 3% target is an informational note in the NEC, not a hard rule, so a slightly longer run is not a code violation by itself, but the load sees less voltage.

Common 50 amp circuits and what they need

Electric range or wall oven

Ranges are 120/240 V appliances, so they need two hots, a neutral and a ground: 6/3 NM-B with ground. A range rated 12 kW or less may be on a 40 A circuit if the nameplate allows; check the installation sheet before you buy cable.

Level 2 EV charger

A charger set to 40 A output is a continuous load, so it needs a 50 A breaker and wire rated at least 50 A: 6/2 NM-B with ground, or 8 AWG THHN in conduit. Hard-wired chargers can often be programmed to 48 A on a 60 A circuit instead.

Subpanel in a garage or shop

Feeders to a subpanel need four conductors (two hots, neutral, ground) and the neutral and ground separated at the subpanel. A detached building also needs its own grounding electrode. Distances here are often long enough that the table above pushes you to 4 AWG copper or 2 AWG aluminum.

RV pedestal (NEMA 14-50)

A 50 A RV service is 120/240 V, four-wire, not a 50 A, 120 V service. Run 6/3 copper or the aluminum equivalent and check the voltage drop: campground pedestals are frequently more than 100 ft from the panel.

Welders, hot tubs and heaters

Welders follow Article 630 and may be allowed smaller conductors based on duty cycle. Hot tubs need a GFCI disconnect within sight of the tub. Electric heaters are continuous loads sized at 125%. Follow the equipment instructions for each.

Sizing a 50 amp run in four steps

1. Confirm the load. Read the appliance nameplate or installation manual. A 50 A breaker does not mean a 50 A load: an EV charger set to 40 A, a range rated 11.5 kW, and a welder with a 45% duty cycle all lead to different conductor sizes.
2. Find the weakest temperature rating. Cable type, breaker and equipment lugs each have a rating. NM-B and UF-B hold you to 60 °C; individual THHN conductors on 75 °C-rated terminals allow the 75 °C column.
3. Pick the smallest size with enough ampacity. At 60 °C that is 6 AWG copper or 4 AWG aluminum; at 75 °C, 8 AWG copper or 6 AWG aluminum.
4. Check voltage drop over the real distance. Measure the cable route, not the straight line: up the wall, across the attic and down again often adds 20–30 ft. Use the distance table above or enter the length in the calculator.

Conduit size for a 50 amp THHN circuit

For a 240 V circuit with a neutral, you pull three insulated conductors plus a 10 AWG ground. Using NEC Chapter 9 Table 5 THHN areas and the 40% fill limit:

• Three 8 AWG THHN (0.0366 in² each) plus one 10 AWG THHN ground (0.0211 in²) total 0.131 in². That is over the 0.122 in² allowed in 1/2 in EMT, so use 3/4 in EMT (0.213 in² at 40%).
• Three 6 AWG THHN (0.0507 in² each) plus the ground total 0.173 in², which also fits 3/4 in EMT.

A 240 V-only circuit with two hots and a ground fits 1/2 in EMT with 8 AWG conductors (0.094 in²). Schedule 40 PVC has a smaller inside diameter than EMT of the same trade size, so check the PVC column if you bury the run.

When aluminum makes sense for 50 amps

For a range or charger 30 ft from the panel, copper NM-B is simpler: the cable is smaller, the device lugs are almost always rated for copper, and the cost difference on a short run is small. Aluminum earns its place on long feeders to a detached garage, barn or RV site. There the voltage drop forces you up two or three sizes anyway, and aluminum SER or URD cable in the larger size often costs less than copper in the smaller one. Use only AA-8000 series conductors, check that every lug is marked AL/CU, and torque each connection to the value printed on the equipment.

Why not 8 AWG NM-B?

Because 8 AWG NM-B is a 40 A cable: the 60 °C column gives 8 AWG copper 40 A. It is one of the most common mistakes on 50 A range and charger circuits, and inspectors look for it. If you want to use 8 AWG on 50 A, it has to be individual THHN/THWN conductors in conduit, landed on breakers and equipment lugs marked 75 °C.

Related calculators and charts

• Wire size calculatorAny breaker, any distance.
• Voltage drop calculatorCheck the drop on your exact run.
• AWG wire gauge chart6 vs 8 AWG side by side, in inches and mm².

Questions people ask

Local amendments, ambient temperature and the number of conductors in a raceway can all change the required size. Confirm with your authority having jurisdiction.