What Size Wire for a 50 Amp Breaker?

Use 6 AWG copper for a 50 amp circuit wired with NM (Romex) cable. 8 AWG copper THHN in conduit can also be used when the breaker and equipment terminals are rated 75 °C. Aluminum needs 6 AWG.

The answer

6 AWG copper

for NM (Romex) cable or 60 °C terminals

8 AWG copper

THHN in conduit with 75 °C terminals

6 AWG aluminum (75 °C terminals)

Wire size for a 50 amp breaker
Case Wire size Table ampacity Area
Copper · 75 °C THHN in conduit, most modern equipment 8 AWG 50 A 8.4 mm²
Copper · 60 °C NM / Romex cable, older terminals 6 AWG 55 A 13.3 mm²
Aluminum · 75 °C Needs connectors and terminals listed for aluminum 6 AWG 50 A 13.3 mm²

Calculate for your exact distance

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How the answer is worked out

The breaker is 50 A. The smallest copper wire with a 75 °C table ampacity at or above 50 A is 8 AWG, rated 50 A, with a cross-section of 8.4 mm².

For 60 °C terminals or NM cable the smallest copper size is 6 AWG, rated 55 A in the 60 °C column.

Aluminum uses its own column. The smallest aluminum size at 75 °C for this rating is 6 AWG, rated 50 A. Aluminum conductors need connectors and terminals listed for aluminum.

NEC 240.4(D) also limits the breaker for small conductors: 14 AWG copper is capped at 15 A, 12 AWG copper at 20 A, 10 AWG copper at 30 A, 12 AWG aluminum at 15 A and 10 AWG aluminum at 25 A. The sizes in the table respect those caps, so a wire is never paired with a breaker larger than its limit.

Why you see both 8 AWG and 6 AWG

The answer depends on the type of wire and the terminal rating. In NEC Table 310.16, 8 AWG copper is rated 50 A in the 75 °C column, which is why 8 AWG THHN in conduit is allowed on a 50 amp breaker when the terminals are rated 75 °C. NM cable (Romex), however, is limited to the 60 °C column by NEC 334.80, where 8 AWG is only 40 A, so a 50 amp circuit wired in NM cable needs 6 AWG (55 A). If the equipment terminals are only rated 60 °C, 6 AWG is also the safe choice.

That is the reason an installer may have run 8 AWG on a 50 amp breaker in conduit, and another may insist on 6 AWG for cable. Both can be right for different installations.

Typical 50 amp circuits

Electric ranges, 50 amp RV outlets, hot tubs and welders commonly use 50 amp circuits. An EV charger that draws 40 A continuous (40 × 1.25 = 50) also needs a 50 amp circuit. Always follow the nameplate of the equipment and your local code.

Aluminum

Aluminum 6 AWG is rated 50 A at 75 °C, so it is the smallest aluminum size for a 50 amp breaker. Use connectors and lugs listed for aluminum, and apply anti-oxidant compound where the manufacturer requires it.

Long runs

The distance table below shows how far each size can go before the drop passes 3% at 50 A. As a guide, 6 AWG copper stays under 3% drop at 50 A and 240 V out to roughly 145 ft, while 8 AWG reaches only about 90 ft. Beyond that, step up to 4 AWG.

How far can you run it? (3% voltage drop)

The distance table uses the same resistance-only model as the calculator, with a 3% limit and the wire at 75 °C. Aluminum has about 1.6 times the resistance of copper for the same size, so an aluminum run of the same length drops more voltage.

Assumes the full 50 A load on a single-phase 240 V circuit, a 75 °C conductor, copper or aluminum, a 3% voltage drop limit and the one-way length in the table. Aluminum shows a dash where that size cannot carry the full current.

Maximum one-way length for 3% drop at 50 A, 240 V, 75 °C conductor
Wire size Copper Aluminum
8 AWG 92.4 ft [28.2 m] —
6 AWG 146.9 ft [44.8 m] 89.2 ft [27.2 m]
4 AWG 233.6 ft [71.2 m] 141.9 ft [43.2 m]
3 AWG 294.6 ft [89.8 m] 178.9 ft [54.5 m]

Need a specific distance? See: What Size Wire for 50 Amps at 100 Feet?

Before you buy wire

The table is a starting point. Work through this list before you order conductors, and keep the answer that matches your real installation.

This is general information based on NEC tables, not a permit or an installation plan. Local amendments, the equipment nameplate and an inspector decide what is acceptable. Read the disclaimer.

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