50 Amp Wire Size: What Gauge for a 50A Breaker?

Short answer: for a 50 amp breaker, use 6 AWG copper if you're running NM-B cable (Romex), or 8 AWG copper THHN/THWN-2 in conduit if every termination is rated 75°C. For aluminum, use 6 AWG aluminum at 75°C (or 4 AWG where you're limited to the 60°C column). Upsize for long runs.

50 amp wire size by wiring method

Wiring method	Copper	Aluminum	Why
NM-B cable (Romex), UF cable	6 AWG (6/3 or 6/2 with ground)	4 AWG	Cable limited to 60°C ampacity (334.80)
THHN/THWN-2 in conduit, 75°C terminals	8 AWG	6 AWG	75°C column of Table 310.16
SER / SE cable, 75°C terminals	8 AWG Cu (rarely stocked)	6 AWG Al	75°C column

Ground wire: 10 AWG copper or 8 AWG aluminum (Table 250.122 for a 50–60 A breaker).

Why two different copper sizes?

The ampacity of a conductor depends on the temperature rating you're allowed to use. 8 AWG copper is rated 40 A at 60°C and 50 A at 75°C. NM-B cable must use the 60°C rating (NEC 334.80), so 8 AWG NM-B is only good for 40 A, and a 50 A circuit needs 6 AWG (55 A at 60°C). Individual THHN conductors in conduit may use the 75°C rating when the breaker, the device and every other termination are listed for 75°C, which makes 8 AWG adequate. That is the 110.14(C)(1)(a) rule: circuits of 100 A or less default to the 60°C column unless the equipment is marked for 75°C.

50 amp wire size by distance

Conductor	50 ft	100 ft	150 ft	200 ft
Copper	8 AWG (1.3%)	8 AWG (2.6%)	6 AWG (2.5%)	4 AWG (2.1%)
Aluminum	6 AWG (1.3%)	6 AWG (2.7%)	4 AWG (2.5%)	3 AWG (2.7%)

Smallest conductor that meets both the 75°C ampacity for a 50 A circuit and a 3% voltage drop at 40 A (80% of the rating), 240 V single-phase, one-way distance. Percent drop in brackets. If the circuit uses NM-B cable or 60°C terminations, start from the 60°C column instead.

A 50 A circuit rarely runs at the full 50 A for long, so the table uses 40 A. If your load really is 50 A continuous, the circuit itself must be larger (see below).

Common 50 amp circuits

Electric range. Most freestanding ranges are on a 40 or 50 A circuit. With NM-B, that's 6/3 copper with ground (range needs a neutral for the 120 V clock and controls).
EV charger. A 50 A circuit supports a charger set to 40 A of continuous current (EV charging is a continuous load, so the circuit must be 125% of the charging current). A NEMA 14-50 receptacle for a portable charger is also common.
RV pedestal, 50 A (NEMA 14-50). 120/240 V with a neutral: 6/3 copper with ground for NM or UF runs. Long runs to an RV pad often need 4 AWG copper or 2 AWG aluminum for voltage drop.
Hot tub / spa. Many need a 50 A GFCI-protected circuit. Follow the manufacturer's installation manual and Article 680.
Subpanel in a garage or shop. A 50 A feeder uses the same sizing, with four wires (two hots, neutral, ground) and a separate grounding electrode at a detached building.

Continuous loads change the answer

If the load runs for 3 hours or more (EV charging, heaters), the breaker and conductors must be rated for 125% of the load. A 40 A continuous load needs a 50 A circuit. A 48 A charger needs a 60 A circuit and conductors; see 60 amp wire size.

Worked example: hot tub 90 feet from the panel

A spa's nameplate calls for a 50 A, 120/240 V circuit and lists a 40 A running load. The feeder runs 90 feet in PVC to a GFCI disconnect beside the tub, then to the spa pack. All terminations are rated 75°C.

Conductor ampacity: 8 AWG copper THHN/THWN-2 is 50 A at 75°C. It qualifies.
Voltage drop at 40 A: 2 × 12.9 × 40 × 90 ÷ 16,510 = 5.63 V, or 2.3% at 240 V. Acceptable.
Upsized alternative: 6 AWG copper gives 2 × 12.9 × 40 × 90 ÷ 26,240 = 3.54 V, or 1.5%, if the manufacturer or the heater's startup behavior calls for margin.
Raceway: two hots and a neutral in 8 AWG plus a 10 AWG ground total 0.1309 in², which fits ¾" PVC Schedule 40 (40% area 0.2032 in²).

Article 680 adds spa-specific rules: an insulated copper equipment grounding conductor for most wiring methods, and a disconnect within sight of the tub but at least 5 feet from its inside wall unless separated by a permanent barrier (680.13). The manufacturer's manual governs the circuit size.

Common mistakes inspectors flag

8/3 NM-B on a 50 A breaker for a range or 14-50 receptacle. NM-B is limited to its 60°C rating: 40 A for 8 AWG.
Missing GFCI protection. The 2023 NEC requires GFCI protection for 125–250 V receptacles in dwelling garages and outdoors (210.8(A)), and 625.54 requires it for receptacles that supply EV chargers.
8 AWG THHN landed on 60°C-rated terminals. The 75°C column requires every termination, including the receptacle, to be rated 75°C.
Undersized EGC on aluminum. A 50 A feeder needs 8 AWG aluminum or 10 AWG copper at minimum.
Neutral and ground bonded at a detached-building subpanel. They must stay separate downstream of the service.

Frequently asked questions

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

Yes, but only as individual 8 AWG copper THHN/THWN-2 conductors (or cable rated for it) with every termination rated 75°C. Not with 8 AWG NM-B cable, which is limited to 40 A.

Is 6 gauge wire good for 50 amps?

Yes. 6 AWG copper is rated 55 A at 60°C and 65 A at 75°C, so it works with any wiring method.

What size wire for a 50 amp RV outlet 100 feet away?

At 100 feet and a 40 A load, 8 AWG copper THHN keeps the drop around 2.6%. With UF or NM cable, 6 AWG copper is the minimum for ampacity and gives about 1.6% drop.

Can I use aluminum wire for a 50 amp circuit?

Yes. 6 AWG aluminum at 75°C (50 A), or 4 AWG where the 60°C column applies. Use terminals rated for aluminum (AL/CU) and follow the torque specs.

Does a 50 amp receptacle in a garage need GFCI protection?

Under the 2023 NEC, yes: 210.8(A) covers 125–250 V receptacles in dwelling garages, and 625.54 separately requires GFCI protection for receptacles installed for EV charging. A hardwired charger provides its own personnel protection under 625.22. Check which edition your jurisdiction enforces.

Last updated: October 6, 2026. Based on NEC 2023; local amendments may differ. Hire a licensed electrician where your jurisdiction requires one.

What Size Wire for a 50 Amp Breaker?