For a standard 50-amp circuit, you need 6 AWG copper wire or 4 AWG aluminum wire. This assumes standard residential conditions: 75°C rated terminations, an ambient temperature of 30°C (86°F), and no more than three current-carrying conductors in a raceway. While pure theory suggests 8 AWG copper might suffice in specific conduit runs, jobsite realities, voltage drop, and equipment listing instructions almost universally mandate 6 AWG copper for 50-amp loads like EV chargers, hot tubs, and subpanels.
• 6 AWG Copper (THHN/THWN): Standard for conduit runs to 50A subpanels and EV chargers.
• 6 AWG Copper (NM-B/Romex): Required for indoor, in-wall 50A runs (e.g., electric ranges).
• 4 AWG Aluminum (XHHW/THHN): Standard for outdoor conduit and long feeder runs to save cost.
• 10 AWG Copper Ground: Minimum equipment grounding conductor for a 50A breaker.
The 50 Amp AWG Wire Sizing Chart (NEC Table 310.16)
The following data is extracted from NEC Table 310.16 (formerly 310.15(B)(16)), the definitive standard for conductor ampacity in the United States. This table assumes an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors bundled together.
How to read this table: Locate your wire material (Copper or Aluminum) and the insulation temperature rating (60°C, 75°C, or 90°C). The intersection gives you the maximum continuous current the wire can safely carry before the insulation degrades or the breaker trips. For 50-amp applications, pay close attention to the 6 AWG and 8 AWG rows, as they straddle the 50A threshold depending on the temperature column.
| AWG Size | Material | 60°C Column (140°F) NM-B, Older Gear |
75°C Column (167°F) THHN, Modern Terminals |
90°C Column (194°F) Derating Starting Point |
|---|---|---|---|---|
| 8 AWG | Copper | 40A | 50A | 55A |
| 6 AWG | Copper | 55A | 65A | 75A |
| 4 AWG | Copper | 70A | 85A | 95A |
| 6 AWG | Aluminum | 40A | 50A | 55A |
| 4 AWG | Aluminum | 55A | 65A | 75A |
| 2 AWG | Aluminum | 75A | 90A | 100A |
Source: NFPA 70 National Electrical Code (NEC), Table 310.16. Always verify against your local AHJ's adopted code year.
Which Temperature Column Applies to Your Installation?
The most common mistake DIYers make is reading the 90°C column because modern THHN wire is stamped with a 90°C rating. You cannot use the 90°C column to determine your base ampacity. Here is how to select the correct column:
1. The 60°C Column (Use for NM-B / Romex)
If you are running standard non-metallic sheathed cable (NM-B, commonly called Romex) through wall cavities, NEC Article 334.80 restricts you to the 60°C column, regardless of the fact that the individual wires inside the sheath might have 90°C insulation. Furthermore, if you are connecting to older equipment or devices explicitly marked for 60°C, you must use this column. Note: 6 AWG copper in the 60°C column is rated 55A, which safely exceeds a 50A breaker.
2. The 75°C Column (Use for THHN in Conduit & Modern Breakers)
If you are pulling individual THHN/THWN-2 conductors through PVC or EMT conduit, and your breaker and termination lugs are rated for 75°C (which almost all modern square-D, Eaton, and Siemens breakers are), you use the 75°C column. Notice that 8 AWG copper is rated exactly 50A here. See the FAQ below for why we still recommend 6 AWG.
3. The 90°C Column (Use ONLY for Derating Calculations)
The 90°C column is strictly used as the starting point for ambient temperature or bundling derating. If you have 4 to 6 current-carrying conductors in a single conduit, you must multiply the base ampacity by 80% (NEC Table 310.15(C)(1)). You start with the 90°C value, apply the 80% multiplier, and then ensure the final result does not exceed the 75°C or 60°C column limits.
What the Ampacity Table Cannot Tell You
NEC Table 310.16 only tells you the thermal limits of the wire insulation. It completely ignores two critical jobsite realities that frequently force electricians to upsize their wire:
Voltage Drop Over Distance
Ampacity tables assume the wire is short enough that resistance doesn't matter. If you are running a 50-amp feeder 150 feet to a detached workshop subpanel, 6 AWG copper will experience a voltage drop exceeding the recommended 3% limit for feeders. At 150 feet, a 48A continuous load on 6 AWG copper drops roughly 6.5 volts (2.7%). While legally permissible, it can cause motors to overheat and lights to dim. For runs over 100 feet at 50 amps, bump up to 4 AWG Copper or 2 AWG Aluminum.
Physical Terminal Limitations
Wire must physically fit into the lugs of your receptacles and breakers. A standard NEMA 14-50R receptacle (used for 50A RV outlets and EV chargers) has deep, heavy-duty lugs designed to clamp down on 6 AWG wire. While an 8 AWG wire might technically fit, the UL listing instructions for many 14-50R receptacles explicitly mandate a minimum of 6 AWG to ensure proper torque and mechanical stability. Per NEC 110.3(B), you must follow the manufacturer's listing instructions, overriding the general ampacity table.
50 Amp AWG Wire FAQ
Can I use 8 AWG wire for a 50 amp breaker?
Technically, yes, but practically, no. According to the 75°C column of Table 310.16, 8 AWG copper THHN in conduit is rated for exactly 50 amps. However, you cannot use 8 AWG NM-B (Romex) because it is restricted to the 60°C column, where 8 AWG is only rated for 40A. Furthermore, most 50-amp receptacles (like the NEMA 14-50) and EV charger manufacturer instructions require a minimum of 6 AWG for proper termination and warranty compliance. To avoid failing an inspection or voiding an equipment warranty, always use 6 AWG copper for 50-amp circuits.
What size ground wire is required for a 50 amp circuit?
According to NEC Table 250.122, the minimum size equipment grounding conductor (EGC) for a 50-amp overcurrent device is 10 AWG copper or 8 AWG aluminum. If you have upsized your current-carrying conductors to mitigate voltage drop (for example, using 4 AWG copper instead of 6 AWG for a long run), NEC 250.122(B) requires you to proportionally increase the size of your ground wire as well.
Does 50 amp AWG wire sizing change for 240V vs 120V?
No. Wire ampacity is a measure of thermal heat dissipation based on current (Amps), not voltage. A 6 AWG copper wire will safely carry 55 amps (at 60°C) whether it is pushing 120V, 240V, or 480V. However, voltage does dictate your insulation rating (most THHN is rated 600V, which covers both) and your voltage drop calculations. A 240V circuit can tolerate twice as much absolute voltage drop as a 120V circuit before hitting the 3% threshold, meaning 240V 50A runs can sometimes stretch slightly further before requiring a wire upsize.
What is the price of 6 AWG copper wire in 2026?
Copper prices fluctuate based on global commodities markets, but as of early 2026, you can expect to pay approximately $1.60 to $2.10 per foot for individual 6 AWG THHN/THWN-2 copper wire purchased on a spool. If you are buying 6/3 NM-B (Romex) with a ground for indoor in-wall use, expect to pay between $3.80 and $4.50 per foot. For long outdoor runs, 4-1-1-2 MH feeder (aluminum) is highly cost-effective, typically running around $1.80 to $2.30 per foot, making it the preferred choice for 50A detached garage subpanels.
