What size wire do I need for a 50 amp breaker?

#6 copper for Romex/NM-B cable, #8 copper THHN in conduit with 75°C terminations, or #6 aluminum — for a 240 V circuit at ordinary distances. Over about 100 feet, upsize for voltage drop.

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

Yes, if it's an individual conductor type like THHN in conduit with 75°C-rated terminations — #8 copper is rated exactly 50 A in the NEC 75°C column. No, if it's NM-B (Romex), which is limited to the 60°C column where #8 is only 40 A.

What size wire for 50 amps at 100 feet?

#6 copper or #4 aluminum keeps voltage drop under the 3% planning target at 240 V and 50 A over 100 one-way feet.

What size wire for a 50 amp hot tub?

#6 copper is the standard answer, run as a 4-wire circuit with GFCI protection and a disconnect within sight of the tub. Long runs from the panel should be checked for voltage drop.

🔌 What Size Wire for 50 Amps?

The internet says 6 gauge AND 8 gauge — both are right, for different wire types. Here's the whole answer.

The short answer

For a 50 amp, 240 V circuit at ordinary distances: #6 copper if you're using Romex/NM-B cable, #8 copper THHN in conduit (with 75°C terminations), or #6 aluminum. Past about 100 feet, voltage drop pushes you bigger — table below.

Why the internet contradicts itself

The two most common answers online are "#6" and "#8," and the argument is really about wire type. The code assigns every wire an amp rating by its insulation temperature column. #8 copper is rated exactly 50 A in the 75°C column — fine for THHN in conduit landing on standard 75°C-rated breaker lugs. But Romex (NM-B cable) must use the 60°C column no matter what's printed on the conductors, and #8 NM-B is only good for 40 A — so Romex needs #6. Sites that say "always #6" are being safe; sites that say "#8" are assuming conduit. Both are quoting real rows of the same table — check it yourself in the ampacity chart guide or the Ampacity Check tool.

Distance changes the answer

Minimum size at 240 V keeping voltage drop under 3%, sized at 50 A (one-way distance):

Material	50 ft	100 ft	150 ft	200 ft	250 ft	300 ft
Copper	8	6	4	4	3	2
Aluminum	6	4	3	2	1	1/0

AWG sizes, computed with our verified calculator engine. Your exact run: Wire Size calculator.

The common 50-amp jobs

Hot tub: usually a 4-wire circuit (two hots, neutral, ground) with a GFCI breaker or GFCI spa disconnect within sight of the tub — #6 copper NM-B indoors transitioning to THHN in conduit outdoors is the classic setup. EV charger: a hardwired charger on a 50 A breaker may deliver at most 40 A continuously (the code requires 125% headroom for loads running 3+ hours), so the conductors must be rated for the 50 A breaker — #6 NM-B or #8 THHN, same as above; check your charger's settings. RV outlet (14-50): same sizing, but if the pedestal is far from the panel, use the distance table — RV pads at 150+ feet routinely need #4. Welder: welders get special treatment (their duty cycle legally allows smaller wire than the breaker suggests — genuinely counterintuitive), so don't panic if a welder manual specifies less.

Worked example: 50 A hot tub at 80 feet

#6 copper (26,240 cmil): drop = 2 × 12.9 × 50 × 80 ÷ 26,240 = 3.9 V = 1.6% of 240 V — comfortably inside 3%. The same run in #8 (16,510 cmil) drops 6.3 V = 2.6% — still legal for THHN, but closer to the line. Run your own numbers in the Voltage Drop calculator.

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