If you need the direct numbers right now for standard residential copper wiring: 14 AWG is 15A, 12 AWG is 20A, 10 AWG is 30A, 8 AWG is 40A, and 6 AWG is 55A. These are the baseline ampacities from the 60°C column, which governs most standard branch circuits and receptacles. But pulling wire is only half the job; sizing it correctly so it doesn't melt inside a conduit or trip a breaker prematurely requires understanding the full chart.
How to Read the NEC Wire Gauge Chart (Table 310.16)
The definitive source for wire sizing in the United States is the NFPA 70 (National Electrical Code), specifically Table 310.16. This table lists the allowable ampacities of insulated conductors rated up to 2000 volts. To use it correctly, you must understand the three temperature columns: 60°C (140°F), 75°C (167°F), and 90°C (194°F).
The 90°C column is not useless, however. It is primarily used as the starting point for derating calculations (adjusting for heat buildup in packed conduits or high ambient temperatures) before you apply the termination temperature cap.
The Master NEC Wire Gauge Chart (Copper Conductors)
Source Standard: NFPA 70 (National Electrical Code), Table 310.16. Values shown are for copper conductors with not more than three current-carrying conductors in a raceway, cable, or earth, at an ambient temperature of 30°C (86°F).
Quick-Jump to Most Queried Sizes: 14 AWG | 12 AWG | 10 AWG | 8 AWG | 6 AWG
| AWG / kcmil | 60°C (140°F) Amps | 75°C (167°F) Amps | 90°C (194°F) Amps | Common Residential Application |
|---|---|---|---|---|
| 14 | 15 | 20 | 25 | 15A Lighting & Receptacle Circuits (NM-B) |
| 12 | 20 | 25 | 30 | 20A Kitchen/Bath/Laundry Receptacles (NM-B) |
| 10 | 30 | 35 | 40 | 30A Dryer, Water Heater, RV Outlet |
| 8 | 40 | 50 | 55 | 40A Range, 50A EV Charger (THHN in conduit) |
| 6 | 55 | 65 | 75 | 60A Subpanel Feeder, 50A Long-Run EV |
| 4 | 70 | 85 | 95 | 100A Subpanel Feeder (Short run) |
| 3 | 85 | 100 | 110 | 100A Subpanel Feeder (Standard) |
| 2 | 95 | 115 | 130 | 125A Subpanel Feeder, Heavy HVAC |
| 1 | 110 | 130 | 145 | 150A Subpanel Feeder |
| 1/0 | 125 | 150 | 170 | 150A Main Service / Subpanel Feeder |
| 2/0 | 145 | 175 | 195 | 200A Main Residential Service |
| 3/0 | 165 | 200 | 225 | 200A Long-Run Service / 225A Feeder |
| 4/0 | 195 | 230 | 260 | 250A Large Estate / Shop Service |
When the Base Chart Fails: Derating and Limitations
The ampacities in Table 310.16 assume ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a raceway. Real jobsites rarely match ideal conditions. Here is how derating rows modify the base value, and what the chart completely ignores.
How Derating Modifies the Base Value
When you bundle more than three current-carrying conductors in a single conduit, the heat cannot dissipate. You must apply a correction factor from NEC Table 310.15(C)(1). For 4 to 6 conductors, you multiply the 90°C ampacity by 80%. For 7 to 9 conductors, you multiply by 70%.
Worked Example: You are pulling four current-carrying 12 AWG THHN wires through EMT conduit to feed two 240V circuits. The base 90°C ampacity for 12 AWG is 30A. Applying the 80% derating factor (30A x 0.80) gives you a derated ampacity of 24A. Because your final termination is on a standard 75°C breaker, you look at the 75°C column (25A) and cap the derated value there. Since 24A is less than 25A, your final allowable ampacity is 24A, which safely allows the use of a 20A breaker.
Similarly, if your attic reaches 45°C (113°F), NEC Table 310.15(B)(1) requires you to multiply the 90°C ampacity by a temperature correction factor of 0.87 before applying any conduit fill derating.
What the Table Cannot Tell You
- Voltage Drop: Table 310.16 only addresses thermal limits (fire safety), not performance. A 10 AWG wire might safely carry 30A without melting, but over a 150-foot run to a detached garage, it will suffer severe voltage drop. You must calculate voltage drop using resistance values from NEC Chapter 9, Table 8, aiming for a maximum 3% drop on branch circuits.
- Conduit Fill: The chart tells you nothing about physical space. To ensure you can actually pull the wire without damaging the insulation, you must check conduit fill percentages using NEC Chapter 9, Table 1, and Annex C.
- Short-Circuit Let-Through: The chart does not account for the magnetic and thermal forces of a dead short. Fault current withstand ratings depend on the specific insulation type and the clearing time of your upstream breaker.
NEC Wire Gauge Chart FAQ
What size wire do I need for a 50 amp breaker?
For a standard 50A circuit (like an EV charger or range) using copper wire in a typical residential setting with 75°C rated terminations, you need 6 AWG copper. The 75°C column lists 6 AWG at 65A, which safely covers the 50A breaker. However, if the run exceeds 50 feet, you should upsize to 4 AWG copper to mitigate voltage drop, especially for continuous loads like EV charging where the 80% continuous load rule (NEC 210.20(A)) effectively requires the wire to handle 62.5A continuously.
Can I use the 90°C column for THHN wire in a residential panel?
Only for the initial math in derating calculations. You cannot use the 90°C column to determine your final breaker size. NEC 110.14(C) dictates that the ampacity is limited by the lowest temperature rating in the circuit. Since almost all residential breakers and receptacles are rated for 60°C or 75°C, your final allowable ampacity is capped at that lower column, even though the THHN insulation itself won't melt until it hits 90°C.
Does the NEC wire gauge chart apply to aluminum wire?
No, the chart provided above is strictly for copper. Aluminum has a higher electrical resistance and requires a larger cross-section to carry the same current safely. If you are using aluminum (commonly XHHW-2 or USE-2 for service entrance feeders), you must use the aluminum columns in Table 310.16. For example, a 200A residential service requires 2/0 AWG copper, but requires 4/0 AWG aluminum (rated 180A at 75°C, which is permitted for a 200A residential dwelling service under NEC 310.12).
How does voltage drop change my wire gauge selection?
The NEC ampacity chart ensures your wire won't catch fire; voltage drop calculations ensure your equipment actually works. The NEC recommends (via Informational Notes in Article 210.19) a maximum 3% voltage drop on the farthest branch circuit and a 5% total drop from the service entrance. If you are wiring a 20A circuit to a shed 120 feet away, 12 AWG wire will result in roughly a 4.5% drop at full load. To stay under the 3% threshold, you must ignore the ampacity chart's minimums and upsize to 10 AWG or 8 AWG purely for performance.
