50 Amp Wire Size: What Gauge Wire Do You Need?
NEC-based wire gauge for a 50 ampbreaker — copper and aluminum sizes, ground wire, conduit, and when to upsize for voltage drop.
For a 50 amp circuit, use #6 AWG copper or #4 AWG aluminum wire (THWN/THHN rated at 75°C).
Based on NEC Table 310.16 (75°C column) and, where noted, Table 310.12 for dwelling services. Confirm termination ratings and local amendments before installing.
50 Amp Wire Size at a Glance
| Copper wire size | #6 AWG |
|---|---|
| Aluminum wire size | #4 AWG |
| Breaker size | 50 amp |
| Ground wire | #10 AWG copper |
| Typical conduit | 3/4" EMT (three #6 THHN conductors); 1" with four conductors |
Verify conduit fill for your exact conductor count and insulation type with the conduit fill calculator.
Common Uses for a 50 amp Circuit
- RV outlets (NEMA 14-50, 50A 120/240V)
- Level 2 EV chargers set to 40A continuous output
- Electric ranges over 12kW
- Hot tubs and spas (50A GFCI-protected)
- Welder circuits and small sub panels
When to Upsize for Voltage Drop
At 240V with a full 50 amp load, #6 copper stays under 3% voltage drop to roughly 110-115 feet. For longer runs — detached garages, RV pads at the back of a property, barn sub panels — upsize to #4 copper (about 180 feet) or #3 copper for very long runs. RV pedestals are a common voltage drop complaint, so check the math before trenching.
The NEC recommends (in informational notes to 210.19 and 215.2) keeping voltage drop under 3% on a branch circuit or feeder and 5% total. Ampacity tables ignore distance entirely, so on any run much past 100 feet, check the numbers with the voltage drop calculator before buying wire.
NEC References and Code Notes
- #6 AWG copper is rated 65A at 75°C in Table 310.16, giving a 50 amp breaker solid margin. #4 AWG aluminum is also rated 65A at 75°C.
- #6 NM-B (Romex) is limited to its 60°C ampacity of 55A — still fine for a 50A circuit, unlike some smaller sizes where the 60°C limit bites.
- Hot tub circuits require GFCI protection per NEC 680.44 and a maintenance disconnect within sight of the tub per 680.12.
- A 50 amp EV charging circuit supports a maximum 40A continuous charger output per NEC 625.41 (125% rule).
- The equipment grounding conductor for a 50 amp circuit is #10 AWG copper per Table 250.122.
See the NEC code reference for related articles. Always confirm requirements with your local authority having jurisdiction.
Frequently Asked Questions
Can I use 8 gauge wire on a 50 amp breaker?
Generally no. #8 AWG copper is rated 50A at 75°C, so it can only qualify when every termination is rated 75°C and no derating applies — and #8 NM-B is limited to 40A, which fails outright. The standard, safe answer for a 50 amp circuit is #6 AWG copper. If any part of the run uses Romex, #6 is required.
What size wire do I need for a 50 amp RV outlet?
A NEMA 14-50 RV outlet on a 50 amp double-pole breaker needs #6 AWG copper (typically 6/3 NM-B with ground, or four #6 THHN conductors in conduit): two hots, a neutral, and a ground. If the pedestal is more than about 100 feet from the panel, upsize to #4 copper for voltage drop.
What size wire for a 50 amp hot tub?
Use #6 AWG copper THHN in conduit from a 50 amp GFCI breaker to the disconnect and on to the spa panel. Most manufacturers prohibit aluminum wire and NM-B cable for spa connections — check the manual. NEC 680 also requires the disconnect to be at least 5 feet from the water, within sight of the tub.
How far can I run 6 gauge wire on a 50 amp circuit?
At 240V and a full 50 amp load, #6 copper reaches roughly 110 feet before exceeding 3% voltage drop. At lower actual loads the distance extends proportionally — a 40A continuous EV charger on #6 gets to about 140 feet. Past those distances, move up to #4 AWG copper.
Related Tools and Wire Size Guides
Wire Sizing Calculator
Calculate the exact wire gauge for any load, voltage, and distance per NEC tables.
Calculate Wire Size →Voltage Drop Calculator
Check whether your run length forces a larger conductor than ampacity alone requires.
Calculate Voltage Drop →Wire Ampacity Chart
Full NEC Table 310.16 ampacities at 60°C, 75°C, and 90°C for copper and aluminum.
View Ampacity Chart →Breaker Size Calculator
Find the right breaker for a given load, including the 125% continuous-load rule.
Size a Breaker →60 Amp Wire Size: What Gauge Wire Do You Need?
For a 60 amp circuit, use #6 AWG copper (rated 65A at 75°C) or #4 AWG aluminum wire.
Read the Guide →100 Amp Wire Size: What Gauge Wire Do You Need?
For a 100 amp feeder or circuit, use #3 AWG copper or #1 AWG aluminum wire (THWN/THHN at 75°C).
Read the Guide →100 Amp Sub Panel Wire Size: What Gauge Feeder Do You Need?
For a 100 amp sub panel, use #3 AWG copper or #1 AWG aluminum feeder conductors with a #8 AWG copper equipment ground (4-wire feeder).
Read the Guide →