What Size Wire for a 50 Amp Breaker? Complete NEC Guide
A 50 amp breaker requires 6 AWG copper or 4 AWG aluminum wire per NEC Table 310.16. This is one of the most common residential high-amperage circuits, used for electric ranges, EV chargers, welders, and hot tubs. Getting the wire size right is critical for safety and code compliance.
The Short Answer: 6 AWG Copper Wire
Per NEC Table 310.16, a 50 amp circuit requires 6 AWG copper wire rated at 65 amps (75°C column) or 4 AWG aluminum wire rated at 65 amps. This applies to standard residential installations using NM-B (Romex) cable, THHN/THWN-2 in conduit, or UF-B for underground runs.
The key factors that determine the correct wire size are the ampacity rating per NEC 310.16, the distance from panel to load (voltage drop), the installation method (cable vs conduit), and the ambient temperature (which may require derating per NEC 310.15).
NEC Table 310.16 — Wire Size Reference
Here is the relevant section of NEC Table 310.16 for copper conductors at 60°C, 75°C, and 90°C temperature ratings:
| AWG | 60°C (NM-B) | 75°C (THWN) | 90°C (THWN-2) | Suitable for 50A? |
|---|---|---|---|---|
| 10 AWG | 30A | 35A | 40A | ❌ No |
| 8 AWG | 40A | 50A | 55A | ⚠️ Only THWN in conduit |
| 6 AWG | 55A | 65A | 75A | ✅ Yes — Standard choice |
| 4 AWG | 70A | 85A | 95A | ✅ Yes — Long runs |
| 3 AWG | 85A | 100A | 115A | ✅ Yes — Extra long runs |
Source: NEC 2023 Table 310.16 — Copper conductors in raceway, cable, or earth
Why Not 8 AWG? Understanding the 60°C Rule
You might notice that 8 AWG THWN (75°C) is rated for 50 amps. However, NM-B cable (Romex) — the most common residential wiring — is rated at the 60°C column, where 8 AWG is only 40 amps. Per NEC 334.80 and 110.14(C), the termination temperature rating (typically 60°C or 75°C) determines which ampacity column to use.
Since most residential breakers and devices have 75°C-rated terminals, you can use the 75°C column for THHN/THWN-2 wire in conduit. But for NM-B cable, you must use the 60°C column, which means 6 AWG is the minimum for 50A.
Voltage Drop for Long Runs
Even when the wire meets ampacity requirements, long runs introduce voltage drop that reduces efficiency and can cause equipment problems. NEC 210.19 (FPN No. 4) recommends keeping voltage drop under 3% for branch circuits and under 5% total.
The voltage drop formula: VD = (2 × L × I × R) / CMA where L is one-way distance (feet), I is current (amps), R is conductor resistivity (10.37 for copper, 17.02 for aluminum), and CMA is wire area in circular mils.
50 Amp Wire Size by Distance
| Distance | Copper (240V) | Aluminum (240V) | Voltage Drop |
|---|---|---|---|
| 0–50 ft | 6 AWG | 4 AWG | < 2.0% |
| 50–75 ft | 6 AWG | 4 AWG | 2.0–3.0% |
| 75–100 ft | 4 AWG | 3 AWG | < 3.0% |
| 100–150 ft | 3 AWG | 2 AWG | < 3.0% |
| 150–200 ft | 2 AWG | 1 AWG | < 3.0% |
| 200+ ft | 1 AWG | 1/0 AWG | < 3.0% |
Based on 50A load at 240V, 3% max voltage drop, copper resistivity 10.37. Verify with our Voltage Drop Calculator.
Common 50 Amp Circuits
Here are the most common household applications that use a 50 amp circuit:
Electric Range / Oven: The most common 50A application. Uses a NEMA 14-50R receptacle (4-prong). NEC 220.55 allows demand factors for household cooking equipment. Most ranges draw 30-50A at peak. See our Electric Range Breaker Guide.
EV Charger (48A): A 48A EV charger (like the Tesla Wall Connector at max power) is a continuous load. Per NEC 625.41: 48A × 1.25 = 60A, which actually requires a 60A breaker. However, a 40A EV charger (32A continuous) works on a 50A circuit. See our Tesla Model 3 Charging Guide.
Welder: Most 240V welders draw 30-50A. NEC 630.12 allows sizing based on duty cycle — a 200A welder at 20% duty cycle may only need conductors rated for the actual input amps.
Hot Tub: Many hot tubs require a 50A GFCI-protected circuit per NEC 680.44. The GFCI must be at the breaker — not at an outlet. See our Hot Tub Breaker Guide.
Sub-Panel Feed: A 50A sub-panel provides enough capacity for a workshop, garage, or small outbuilding. Requires 4 conductors (2 hots + neutral + ground) with a separate ground bar in the sub-panel.
Installation Requirements per NEC
NEC 110.14(C) — Temperature Limitations: Conductor ampacity must be determined by the lowest temperature rating of any connected termination, conductor, or device. For most residential equipment with 75°C terminals, use the 75°C column of NEC 310.16.
NEC 210.20 — Continuous Load (80% Rule): If the load is continuous (3+ hours), the circuit must be rated at 125% of the load. This means a 50A breaker can carry a maximum continuous load of 40A. For a 50A continuous load, you would need a 60A or larger breaker.
NEC 240.4 — Overcurrent Protection: The wire must be protected by an overcurrent device that does not exceed its ampacity. 6 AWG copper at 55A (60°C) or 65A (75°C) can be protected by a 50A breaker per NEC 240.4(B) small conductor rules.
NEC 250.122 — Equipment Grounding: A 50A circuit requires a minimum 10 AWG copper equipment grounding conductor per NEC Table 250.122. When using NM-B cable (6/3 NM-B), the bare ground wire is included.
Parts List for a 50 Amp Circuit
Everything you need for a standard 50A/240V installation:
From the panel to the device (under 75 feet):
1. 50A double-pole breaker — must match your panel brand (Square D, Eaton, Siemens, etc.)
2. 6/3 NM-B cable (Romex) for interior runs, or 6 AWG THHN/THWN-2 wire in conduit for exposed/exterior runs
3. NEMA 14-50R receptacle (4-prong) for ranges/EV chargers, or NEMA 6-50R (3-prong) for welders
4. 4-11/16" deep metal box for the receptacle (required for the wire bending radius)
5. Cable clamps, wire nuts, and appropriate box connectors
Can I Use Aluminum Wire for a 50 Amp Circuit?
Yes. Aluminum is cheaper and lighter than copper. For a 50A circuit, use 4 AWG aluminum (rated 65A at 75°C per NEC 310.16). However:
All connections must use AL/CU rated devices and terminals. Apply anti-oxidant compound to all aluminum connections to prevent corrosion. Aluminum expands more than copper under heat, so all connections must be torqued to manufacturer specifications. For most homeowners, the convenience and reliability of copper makes it the better choice despite the higher cost.
Disclaimer: This article is for educational reference only. All electrical work should be performed by or under the supervision of a licensed electrician. Local codes may differ from the NEC. Always obtain permits and inspections for new electrical circuits.