Wire Size for 50 Amp Circuit

Find the copper or aluminum wire for a 50 amp breaker and check the voltage drop for your run length.

Assumes NEC 2023 Table 310.16: copper or aluminum, up to 3 current-carrying conductors in a raceway or cable, 30 °C ambient, 60 °C terminals for a 50 A circuit (110.14(C)), 3 % drop target; ground wire not included. Free, runs in your browser. Verify with your local code and a licensed electrician before you install.

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The wire size for 50 amp circuits is at least 6 AWG copper or 4 AWG aluminum when the terminals are treated as 60 °C, which is how most circuits of 100 A or less are judged. Enter your own breaker, load and run length and the calculator checks two limits: the wire’s allowed ampacity must reach the breaker rating, and the voltage drop over the one-way run must stay inside your target. With its starting values (a 40 A load on 240 V over 60 ft of copper), the answer is 6 AWG with a 0.98 % drop. The result also names the deciding limit, gives the copper and aluminum sizes side by side, and shows how far the recommended size can run before the drop passes your target.

How to use the 50 Amp Wire Size Calculator

Keep 50 in “Breaker rating (A)”, or type the rating printed on your breaker.
Enter the nameplate or calculated current in “Load current (A)”. Leave it empty and the wire is sized for the full breaker rating.
Tick “Continuous load (3 hours or more)” for loads such as an EV charger or a hot tub heater. The design current then becomes 125 % of the load.
Pick the “Supply type” and enter “Voltage (V)”: 240 for most 50 A residential circuits, or the line-to-line voltage for three phase.
Type the “One-way length” in ft or m, measured along the cable route from the panel to the load.
Choose Copper or Aluminum under “Conductor” and the “Insulation temperature rating” printed on the cable, for example 60 °C for NM-B.
Leave “Allowed voltage drop (%)” at 3 unless your project sets another limit.
Open the advanced settings only when they apply: “Terminal temperature rating” (keep Auto unless the equipment is listed for 75 °C), “Ambient temperature” and “Current-carrying conductors in the raceway or cable”.
Read “Recommended wire size” and “Deciding limit”, then the steps and warnings below the result.

The example buttons above the form load a range, an EV charger, an RV pedestal, an aluminum subpanel or a hot tub. “Copy result”, “Copy link” and “Print / save as PDF” keep the answer, and Reset restores the starting values.

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

With the terminal setting left on Auto, the calculator answers 6 AWG in copper and 4 AWG in aluminum. Both sizes have an allowed ampacity of 55 A once the 60 °C terminal limit of NEC 110.14(C)(1) is applied, which covers the 50 A breaker. A longer run can still push the answer up a size.

The calculator checks the sizes in this order:

The conductor must be protected by the breaker, so its allowed ampacity has to be at least 50 A (NEC 240.4 and 310.16).
The insulation column gives the starting value, and the ambient factor (310.15(B)(1)) and the factor for more than three current-carrying conductors (310.15(C)(1)) reduce it.
The terminal column caps the result. For copper 6 AWG the steps show 65 A in the 75 °C column, cut to 55 A by 60 °C terminals.
Voltage drop at your load current is checked last, and the larger of the two sizes wins.

Why can both 6 AWG and 8 AWG be recommended for 50 amps?

The difference is the terminal rating. With Auto, copper 8 AWG fails because 60 °C terminals limit it below 50 A, so the tool picks 6 AWG. Set “Terminal temperature rating” to 75 °C, which is allowed only when the breaker and the equipment are listed for it, and 8 AWG copper passes at 50 A.

Settings (50 A breaker, 40 A load, 240 V, 60 ft)	Copper	Aluminum
Terminal rating Auto	6 AWG	4 AWG
Terminal rating 75 °C (listed equipment)	8 AWG	6 AWG

NM-B cable is a separate case: its 60 °C insulation keeps it in the 60 °C column (NEC 334.80), so 6 AWG NM-B is the minimum whatever the terminals are.

How far can you run 50 amp wire at 240V?

At a full 50 A load on 240 V, 6 AWG copper reaches about 147 ft one way before the drop passes 3 %. At a 40 A load it reaches about 184 ft. Beyond those distances the calculator moves up to 4 AWG copper because of voltage drop, not ampacity.

6 AWG copper, 240 V	One-way length	Voltage drop
40 A load	50 ft	0.817 %
40 A load	60 ft	0.98 %
50 A load	100 ft	2.04 %
50 A load	150 ft	over 3 %, so 4 AWG at 1.93 %

Voltage matters only here. The same 40 A over 50 ft drops 1.63 % at 120 V against 0.817 % at 240 V, while the ampacity answer stays 6 AWG.

Worked examples

Input	Result
50 A breaker, 40 A load, 240 V, 60 ft, copper 75 °C	6 AWG (0.98 %)
50 A breaker, 40 A load, 240 V, 30 ft, copper 75 °C	6 AWG (0.49 %)
50 A breaker, 40 A load, 240 V, 40 ft, copper 60 °C	6 AWG (0.653 %)
50 A breaker, 45 A load, 240 V, 150 ft, aluminum 75 °C	4 AWG (2.85 %)
50 A breaker, 40 A load, 120 V, 50 ft, copper 75 °C	6 AWG (1.63 %)

Calculated by the tool above; open it with the same values to see each step.

Questions, briefly answered

Is 8 gauge wire enough for 50 amps?

Not with the Auto setting. Copper 8 AWG has 50 A in the 75 °C column but only 40 A in the 60 °C column, and Auto applies 60 °C terminals to circuits up to 100 A. It passes only when the equipment is listed for 75 °C and the cable is not NM-B.

Is 8 AWG aluminum enough for 50 amps?

No. Aluminum 8 AWG stays below 50 A in every terminal setting the tool offers, so its aluminum answer is 4 AWG with Auto and 6 AWG with listed 75 °C terminals.

How far can I run 6 gauge wire at 50 amps?

About 147 ft one way at 240 V with a full 50 A load and a 3 % drop target. Change the load or the target and the “Longest run of the recommended size” row updates.

Will 12/2 wire carry 50 amps?

No. NEC 240.4(D) limits 12 AWG copper to a 20 A breaker, so it cannot be used on a 50 A circuit.

Can I use 6 AWG aluminum for 50 amps?

Only with terminals listed for 75 °C. Under Auto the 60 °C limit leaves it short of 50 A, so the tool gives 4 AWG aluminum. Aluminum also needs lugs and connectors marked AL/CU.

Is 3% voltage drop a requirement?

No. The 3 % for a branch circuit and 5 % in total come from informational notes in the NEC, which are advice rather than rules. You can change “Allowed voltage drop (%)” to any target.

What size wire do I need for a 50 amp EV charger circuit?

A charger drawing 40 A is a continuous load, and 40 A × 125 % = 50 A fits a 50 A breaker. The “EV charger, 40 A continuous” example gives 6 AWG copper at 0.98 % over 60 ft.

What about a true 50 amp continuous load?

It needs a larger circuit. 50 A × 125 % = 62.5 A is above the breaker, and the tool warns that the breaker would trip.

Wire Size for 30 Amp Circuit: for dryers, water heaters and 30 A RV hookups.
Wire Size for 60 Amp Circuit: for 60 A subpanels and larger EV chargers.
Wire Size Calculator: for any breaker or load, including watts and three phase.
Wire Ampacity Calculator: to see how much current one wire size can carry under your conditions.
Voltage Drop Calculator: to check the drop of a wire size you already have.
Electrical Load Calculator: to find whether a new 50 A circuit fits your service.
Conduit Fill Calculator: to pick the conduit for the conductors you chose.
Wire and Cable Calculators: every wire sizing tool on the site.

Updated October 2026