50 Amp Wire Size

6 AWG copper

For a 50 A breaker with NM-B cable (60 °C). Where the 75 °C column applies, such as THHN in conduit with 75 °C terminals, 8 AWG copper is allowed. In aluminum: 4 AWG at 60 °C, 6 AWG at 75 °C.

Smallest wire for a 50 A breaker, NEC 2026 Table 310.16 and 240.4(D). 30 °C ambient, up to three current-carrying conductors.
Wire and column	Smallest size	Allowed amps
Copper, 60 °C	6 AWG	55 A
Copper, 75 °C	8 AWG	50 A
Aluminum, 60 °C	4 AWG	55 A
Aluminum, 75 °C	6 AWG	50 A

How length changes the answer

Recommended AWG for 50 A at 240 V single phase, by one-way length: the larger of the ampacity size and the size that keeps voltage drop within 3%.
Length, one way	Copper, 60 °C	Copper, 75 °C	Aluminum, 60 °C	Aluminum, 75 °C
25 ft	6	8	4	6
50 ft	6	8	4	6
75 ft	6	8	4	6
100 ft	6	6	4	4
150 ft	4	4	3	3
200 ft	4	4	2	2

Check your own circuit in the wire size calculator

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A 50 amp breaker takes 6 AWG copper when the circuit runs in NM-B cable, the usual house wiring. NEC 334.80(A) (334.80 in the 2023 edition) holds NM-B to its 60 °C ampacity, and in that column 6 AWG copper carries 55 A, enough for the 50 A breaker with a little to spare. The size below it, 8 AWG, carries only 40 A at 60 °C.

That gap is why 8 gauge is the usual argument at 50 A. Table 310.16 does list 8 AWG copper at exactly 50 A, but that is its 75 °C rating, and it counts only when the whole circuit is rated 75 °C: individual conductors such as THHN in conduit, a breaker with 75 °C terminals, and equipment whose terminals are marked 75 °C too. In NM-B, 8 gauge on a 50 A breaker is 10 A short. If the run is cable, or the terminal ratings can't be confirmed, the size is 6 AWG. Your electrician or inspector can confirm the ratings from the markings on the breaker and the equipment.

Common 50 A circuits in a home are a NEMA 14-50 receptacle and an electric range. The 14-50 is a 50 A, 125/250 V, four-wire grounding receptacle: two hots, a neutral and a ground. It is the 50 A outlet NEC 551.71(A) requires at RV sites (551.71(B) and (C) in 2023), and some plug-in EV chargers are made to plug into one. For ranges, the NEC sets a 40 A minimum branch circuit for a range of 8¾ kW or more (210.19(C)); putting a range on 50 A is common practice rather than a code minimum, and the range's nameplate and installation instructions decide which it needs.

EV charging is where the 125% rule matters. The 2026 NEC treats EV charging as a continuous load (625.41), and a circuit for a continuous load is sized at 125% of it: 210.19(A)(1) for the wire and 210.20(A) for the breaker. In the 2023 edition the same rules were 625.41 and 625.42. Turned around, a 50 A breaker can serve at most 40 A of continuous load. So a charger set to 40 A goes on a 50 A circuit, while a 48 A charger needs a 60 A circuit and 4 AWG copper in NM-B. The same 40 A ceiling holds for any other continuous load on a 50 A circuit.

Distance is the other reason to go up a size. At 240 V and the full 50 A, 6 AWG copper loses 4.80 V over a 100-foot run, 2%, leaving 235.2 V at the load, which is inside the 3% the NEC's informational notes suggest for a branch circuit. At 150 and 200 feet the length table moves copper to 4 AWG in both columns. Length also cancels the 75 °C saving: 8 AWG copper keeps within 3% out to 75 feet, but by 100 feet it has to be 6 AWG. The 3% figure is a recommendation, not a requirement, and a long run out to a detached garage or an RV pad is where it is most likely to decide the size.

Aluminum runs larger for the same breaker: 4 AWG at 60 °C or 6 AWG at 75 °C, rated 55 A and 50 A. Aluminum also needs a breaker and receptacle or appliance terminals marked AL or CU/AL; a terminal marked for copper only can't take it.

Frequently asked questions

Can I use 8 gauge wire on a 50 amp breaker?

Not in NM-B cable: at 60 °C, 8 gauge copper is good for 40 A, so 8 gauge NM-B on a 50 A breaker isn't allowed, and the answer is 6 AWG. With individual conductors such as THHN in conduit, and a breaker and equipment rated 75 °C at their terminals, 8 AWG copper is rated 50 A, exactly the breaker size, so it may be used.

What size wire for a 50 amp RV outlet?

6 AWG copper in NM-B, with four conductors (two hots, a neutral and a ground), because the 50 A RV receptacle, the NEMA 14-50, is a 125/250 V four-wire device. With THHN in conduit and 75 °C terminals, 8 AWG copper is enough, and it stays within 3% voltage drop out to 75 feet. For a longer run out to an RV pad, copper goes to 4 AWG at 150 feet.

What size aluminum wire for 50 amps?

4 AWG aluminum at 60 °C, or 6 AWG where the 75 °C column applies. Distance pushes it up too: at 240 V, keeping within 3% takes 3 AWG aluminum at 150 feet and 2 AWG at 200 feet.

What size wire for 50 amps at 150 feet?

4 AWG copper, whether the run is NM-B or THHN in conduit. 6 AWG has the ampacity, but at 150 feet and 240 V its voltage drop lands just over 3%, so the length table moves it to 4 AWG. In aluminum, 3 AWG.

What breaker and wire does a 40 amp EV charger need?

A 50 A breaker with 6 AWG copper in NM-B, or 8 AWG copper where the 75 °C column applies. EV charging is a continuous load, so the circuit is sized at 125% of the charger's 40 A, which is 50 A.