What Size Wire for 50 Amps?

A 50-amp circuit needs 6 AWG copper or 4 AWG aluminum. The math: 50 A × 1.25 (continuous rule) = 62.5 A required ampacity. At the 75°C column of NEC Table 310.16, 6 AWG copper carries 65 A — the smallest size that clears 62.5 A. Aluminum steps up to 4 AWG (65 A).

That covers most 50-amp uses: electric ranges, hot tubs and spas, welders, RV pedestals, and 50 A EV chargers. But run length matters. On circuits longer than roughly 100–150 feet, voltage drop can push the recommendation to 4 AWG copper even though 6 AWG passes ampacity. The calculator above checks both so you get the right answer for your specific run.

One point of confusion worth clearing up immediately: the "50" in a 50-amp circuit refers to the breaker rating, not the wire's ampacity. Because 8 AWG copper happens to be rated 50 A at 75°C, people assume it is the "50-amp wire." It is not — the continuous-load rule requires the conductor to have ampacity of 62.5 A, which lands on 6 AWG. Reserve 8 AWG for 40-amp circuits, and treat 6 AWG copper (or 4 AWG aluminum) as the default 50-amp conductor unless a long run or heavy derating calls for more.

The reason a 50-amp breaker does not use a "50-amp wire" is the NEC continuous-load rule. A load running at full current for three hours or more must have its conductor and breaker sized at 125% of that current (NEC 210.20, 215.3). Equivalently, a conductor may only be loaded to 80% of its ampacity.

Reading down the 75°C copper column: 8 AWG is 50 A (too small — below 62.5), and 6 AWG is 65 A (passes). So 6 AWG copper is the answer. Note the coincidence people misread: 8 AWG is rated exactly 50 A, which tempts installers to use it for a "50 amp" circuit — but ampacity is not the same as breaker size once the 125% rule applies. Reserve 8 AWG for 40-amp circuits.

If the 50-amp load is genuinely non-continuous (short-duration only), 8 AWG can be permissible, but ranges, EV chargers, and spas are treated as continuous by convention and inspectors, so 6 AWG is the safe standard. Always verify the breaker with the breaker size calculator.

Example 1 — 50 A range, 30 ft copper: required = 62.5 A → 6 AWG. Voltage drop = 2 × 30 × 50 × 0.491 ÷ 1000 = 1.47 V = 0.61% of 240 V. Comfortably under 3%. Answer: 6 AWG copper.

Example 2 — 50 A hot tub, 120 ft copper: 6 AWG still meets ampacity, but drop = 2 × 120 × 50 × 0.491 ÷ 1000 = 5.89 V = 2.45%. Under 3%, so 6 AWG works — barely. At 160 ft it would exceed 3%, so 4 AWG becomes the better choice.

Example 3 — 50 A subpanel, 100 ft aluminum: aluminum needs 4 AWG for ampacity. Drop = 2 × 100 × 50 × 0.508 ÷ 1000 = 5.08 V = 2.12%. Fine at 100 ft, but aluminum's higher resistance means a 175 ft run would push over 3% and want 2 AWG.

Example 4 — 50 A EV charger, 60 ft copper: 6 AWG, drop = 2 × 60 × 50 × 0.491 ÷ 1000 = 2.95 V = 1.23%. Well within limits. Many EV installers still pull 4 AWG to future-proof for an eventual 60-amp charger.

Example 5 — 50 A welder, 45 ft copper, intermittent: a welder is a genuine non-continuous load, so the 125% rule can be relaxed and 8 AWG (50 A) is technically permissible. In practice most electricians still install 6 AWG for a 50 A welder receptacle because the receptacle and breaker are rated 50 A and the extra margin costs little. Voltage drop at 6 AWG here is 2 × 45 × 50 × 0.491 ÷ 1000 = 2.21 V = 0.92% — negligible. The takeaway: even when code would allow a smaller wire for intermittent duty, matching the wire to a 50 A receptacle keeps the installation simple and inspection-friendly.

The 50-amp circuit is one of the most common high-power residential circuits. Typical loads and notes:

• Electric range / oven — 6 AWG copper; ranges often use 6/3 NM-B cable with ground.
• Hot tub / spa — 6 AWG copper on a GFCI breaker; watch run length from panel to disconnect.
• Level 2 EV charger (40 A output) — a 40 A charger on a 50 A breaker uses 6 AWG (charger draws 40 A continuous → 50 A breaker).
• RV pedestal (50 A) — 6 AWG copper for the 240 V/50 A NEMA 14-50 outlet.
• Welder — often intermittent duty, but 6 AWG is the safe default for a 50 A receptacle.
• Subpanel — a 50 A subpanel feeder uses 6 AWG copper (or 4 AWG aluminum), with a separate ground and isolated neutral.

Cable type matters: NM-B (Romex) ampacity is taken from the 60°C column, but 6 AWG NM-B is still rated for 50-amp use in practice because 6/3 is manufactured to 55 A at 60°C. For conduit installs, THWN-2 in 6 AWG is standard. Confirm raceway fill with the conduit fill calculator.

Ampacity says 6 AWG; voltage drop sometimes overrules it. The recommended limit is 3% for a branch circuit, computed as:

For 6 AWG copper (0.491 Ω/1000 ft) at 50 A on 240 V, the 3% ceiling (7.2 V) is reached at about 147 feet one-way. Beyond that, upgrade to 4 AWG (0.308 Ω), which pushes the 3% limit out past 230 feet. Aluminum, with ~1.6× the resistance, hits the wall sooner and upsizes earlier.

This is the single most overlooked factor in DIY 50-amp installs — a hot tub 180 feet from the panel wired in 6 AWG will run, but the heater and pump see reduced voltage, drawing more current and running hotter. Use the calculator's live drop readout, or the dedicated voltage drop calculator, to decide when to jump to 4 AWG.

Because voltage drop grows with distance, the correct 50-amp conductor is really a function of how far the circuit runs. The table below turns the drop math into a plain lookup for copper at 240 V, using the 3% branch-circuit target. Use it as a sanity check against the live result above.

The pattern is clear: 6 AWG copper is fine for the great majority of household 50-amp circuits, which are usually within 100 feet of the panel. Only when a spa, detached shop, or RV pedestal sits far from the panel does the run push you to 4 AWG or larger. Aluminum, carrying about 1.6 times the resistance of copper, reaches each threshold at roughly two-thirds of the distance, so an aluminum 50-amp circuit upsizes one step sooner than the copper figures shown.

1. Leave amps at 50 (or change it to size a nearby circuit like 40 A or 60 A).
2. Enter the one-way run length from panel to load. This drives the voltage-drop check that decides between 6 AWG and 4 AWG.
3. Pick copper or aluminum. Copper 6 AWG or aluminum 4 AWG is the standard 50-amp pairing.

Read the recommended AWG, the required ampacity (62.5 A for 50 A), and the voltage drop. If the note warns you are over 3%, step up a size. Then confirm the breaker and outlet — a 50-amp circuit uses a 50 A double-pole breaker and, for outlets, a NEMA 14-50 or 6-50 receptacle depending on whether a neutral is needed.

Getting the conductor gauge right is only part of a code-compliant 50-amp circuit. The cable type, grounding conductor, and receptacle all have to match.

Cable type. For a conduit install, pull individual 6 AWG THWN-2 conductors. For a cable install, 6/3 NM-B (Romex) carries two hots, a neutral, and a ground and is rated for 50 A range and RV use. In wet or outdoor locations, use UF-B or conduit with THWN-2. Never bury bare NM-B; it is for dry, indoor use only.

Equipment grounding conductor. Per NEC Table 250.122, a 50 A circuit uses a 10 AWG copper (or 8 AWG aluminum) equipment ground. In 6/3 NM-B the included ground is usually 10 AWG, which satisfies this. The ground is not part of the ampacity or fill-current calculation but must be present and correctly sized.

Receptacle and breaker. A 50 A circuit uses a 50 A double-pole (240 V) breaker. Choose the receptacle by load: a NEMA 14-50 (four-wire: two hots, neutral, ground) serves ranges, RV pedestals, and EV chargers that need 120 V accessories; a NEMA 6-50 (three-wire: two hots, ground) serves welders and pure-240 V equipment. Match the plug on the appliance to the receptacle — mixing 14-50 and 6-50 is a frequent field error.

GFCI protection. Hot tubs, spas, and many outdoor 50-amp circuits require GFCI, either a GFCI breaker or a spa-panel disconnect with built-in GFCI. Confirm the breaker choice with the breaker size calculator and the conduit fit with the conduit fill calculator.

• Using 8 AWG because it is "rated 50 A." The 125% continuous rule requires 62.5 A, so 6 AWG is the correct size for typical 50-amp loads.
• Ignoring long-run voltage drop. Past ~150 feet, 50 A on 6 AWG copper exceeds 3% — go to 4 AWG.
• Skipping the GFCI requirement. Hot tubs, spas, and many outdoor 50-amp circuits require GFCI protection.
• Undersizing the ground or neutral. Follow NEC 250.122 for equipment grounding conductor sizing on a 50 A circuit (typically 10 AWG copper).
• Wrong receptacle. NEMA 14-50 (4-wire) for ranges/RVs/EVs needing neutral; 6-50 (3-wire) for welders and some equipment.

For adjacent sizes see wire size for 100 amps, and for the general method use the wire size calculator.