What Size Wire for a 50 Amp Circuit? (Copper & Aluminum)

"What size wire for a 50 amp circuit?" has a clean standard answer — 6 AWG copper (or 4 AWG aluminum) — but the popular shortcut answers online skip the two things that actually matter: the terminal temperature rating your breaker uses, and the continuous-load rule that applies to EV chargers. Get those wrong and you can undersize a circuit that runs hot for hours. This guide gives you the correct sizing, the reasoning behind it, and the common 8-gauge trap to avoid.

The short answer

For a standard 50-amp, 240-volt circuit:

• Copper: 6 AWG
• Aluminum / copper-clad aluminum: 4 AWG

That's the size for a 50A breaker feeding a range, electric dryer, welder, hot tub, RV outlet, sub-panel, or a NEMA 14-50 receptacle for an EV charger. Along with the two hot conductors you'll also run a neutral (where required) and an equipment ground, sized per code.

Why 6 AWG and not smaller? It comes down to the temperature rating electricians actually use.

Why the temperature rating decides it

Every wire has an ampacity — the current it can safely carry — and that number changes with the insulation's temperature rating. The National Electrical Code (NEC) publishes three columns: 60°C, 75°C, and 90°C. Here's the catch: even if your wire's insulation is rated 90°C, you're limited by the lowest-rated part of the circuit — and most breakers and receptacles are rated 75°C. So for a 50A household circuit, you size to the 75°C column.

At the 75°C rating:

And aluminum, which carries less current per gauge:

Six-gauge copper at 65 amps sits comfortably above a 50A breaker. That margin is exactly why it's the standard.

The 8-gauge trap

You'll see plenty of forum answers saying "8 AWG copper is fine for 50 amps." Technically 8 AWG copper is rated 50 amps — but only at the 75°C column, with zero margin, and it drops to just 40 amps at the 60°C rating. If any part of your circuit (an older breaker, a 60°C-rated terminal) falls to the 60°C column, 8 AWG is no longer legal for 50 amps.

Worse, an EV charger is a continuous load (more on that below), and running a wire at exactly its rated ampacity for hours is precisely what the code's safety margins exist to prevent. For a real 50A circuit, run 6 AWG copper. It's the size professionals use, it has margin, and it stays legal across terminal ratings. The few dollars of extra copper are cheap insurance against a wire that runs hot.

The EV-charger exception: continuous loads

Here's where 50-amp sizing gets its own wrinkle. Most 50A loads — a range, a dryer — are not continuous (they don't run at full current for 3+ hours). An EV charger is continuous, and the NEC requires continuous-load circuits to be sized at 125% of the load. That changes how you read the numbers:

• A 40-amp charger is a 40A continuous load → 40 × 1.25 = 50A required capacity → 50A breaker + 6 AWG copper. This is the most common home EV-charger install, and 6 AWG handles it.
• A charger that actually draws 50 amps continuously needs 50 × 1.25 = 62.5A of capacity → a 60A (or larger) breaker and wire sized accordingly — you've moved past a "50 amp circuit."

So the rule of thumb: size an EV circuit to the charger's continuous output, not just to the breaker on the wall. A 50A breaker with 6 AWG copper is correct for a 40A charger. If you're planning an EV charger specifically, the full walkthrough is in EV charger breaker & wire sizing: the NEC 125% rule, and you can confirm your exact breaker and wire with the Level 2 charger breaker size calculator.

Quick reference: common circuit sizes

For the full chart of gauges, breakers, and terminal ratings, see the wire & breaker size reference, and for outlet types the NEMA plug chart.

A few install cautions

• Wire length matters. Long runs (roughly 100+ feet) may need an upsize to counter voltage drop. This guide covers standard runs; size up for long distances.
• Aluminum needs the right terminations and anti-oxidant where required — it's fine when done correctly, but it's not a drop-in for copper.
• Always match the breaker to the wire, never above it. The breaker protects the wire; a breaker larger than the wire's ampacity defeats that protection.
• This is a permit-and-inspection job. A 240V 50A circuit should be installed by a licensed electrician to local code. Use this guide to understand the sizing, not to skip the professional.

The bottom line

A 50-amp circuit needs 6 AWG copper or 4 AWG aluminum in the vast majority of installs — that's the standard, code-safe size at the 75°C terminal rating your breaker uses. Skip the "8 gauge is fine" shortcut: it has no margin and fails the 60°C rating. And remember the EV exception — a charger is a continuous load, so a 40A charger belongs on a 50A breaker with 6 AWG copper, while a true 50A-continuous charger moves you up to a 60A circuit. When in doubt, size the wire generously and let a licensed electrician confirm the install. Planning an EV charger? Check your exact numbers with the calculators below.