For standard 120V and 240V residential branch circuits, the most common AWG sizes are 14 AWG (15 amps), 12 AWG (20 amps), and 10 AWG (30 amps). For larger feeder circuits supplying subpanels or heavy appliances, 6 AWG (50-60 amps), 4 AWG (70-85 amps), and 2 AWG (95-115 amps) are the standard benchmarks. These values assume copper conductors with standard insulation ratings and standard ambient temperatures.
How to Read the NEC AWG Size Ampacity Table
The ampacity of a wire is not a single fixed number; it changes based on the temperature rating of the wire's insulation and the terminals it connects to. The table below is derived directly from NEC Table 310.16, which governs copper conductors rated up to 2000 volts.
NEC Section 110.14(C) dictates the temperature column you must use. For circuits rated 100 amps or less (or using 14 AWG through 1 AWG wire), you must use the 60°C (140°F) column unless the equipment is specifically marked and rated for 75°C. For circuits over 100 amps (or 1/0 AWG and larger), you use the 75°C (167°F) column. The 90°C column is almost never used for final breaker sizing; it is reserved strictly as the starting baseline for calculating derating adjustments.
Complete AWG Size Reference Chart
📌 Quick Jump: Looking for 12 AWG (20A outlets)? See Row 2. Looking for 10 AWG (30A dryers)? See Row 3. Looking for 6 AWG (50A ranges/EV chargers)? See Row 5. Looking for 4/0 AWG (200A main service)? See Row 13.
| AWG Size | 60°C (140°F) Ampacity | 75°C (167°F) Ampacity | 90°C (194°F) Ampacity | Max Standard Breaker (NEC 240.4) |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | 15A |
| 12 AWG | 20A | 25A | 30A | 20A |
| 10 AWG | 30A | 35A | 40A | 30A |
| 8 AWG | 40A | 50A | 55A | 40A |
| 6 AWG | 55A | 65A | 75A | 60A |
| 4 AWG | 70A | 85A | 95A | 80A |
| 3 AWG | 85A | 100A | 115A | 100A |
| 2 AWG | 95A | 115A | 130A | 125A |
| 1 AWG | 110A | 130A | 145A | 150A |
| 1/0 AWG | 125A | 150A | 170A | 150A |
| 2/0 AWG | 145A | 175A | 195A | 175A |
| 3/0 AWG | 165A | 200A | 225A | 200A |
| 4/0 AWG | 195A | 230A | 260A | 225A / 250A* |
*Note: 4/0 AWG copper at 75°C is rated for 230A. NEC 240.4(B) allows rounding up to the next standard breaker size (250A) for feeder conductors, but 200A is the standard residential service disconnect size.
What the AWG Size Table Cannot Tell You
The chart above assumes ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors bundled together. In real-world installations, you must adjust for physical constraints.
How Derating Rows Modify the Base Value
When you pull more than three current-carrying conductors through a single raceway or conduit, the wires heat each other up. NEC 310.15(C)(1) requires you to derate the ampacity using the 90°C column as your starting baseline.
Worked Example: You are pulling four 12 AWG THHN current-carrying conductors in one conduit for a multi-wire branch circuit. The base 90°C ampacity for 12 AWG is 30A. The derating factor for 4-6 conductors is 80%.
30A × 0.80 = 24A.
Because 24A is still greater than the 20A maximum breaker size for 12 AWG (per NEC 240.4(D)), you can still use a 20A breaker. However, if you had 10 conductors in the pipe (50% derating factor), the math becomes 30A × 0.50 = 15A. You would be forced to either downgrade the breaker to 15A or upsize the wire to 10 AWG. Always consult OSHA electrical safety guidelines and local AHJ rules when bundling conductors in commercial or dense residential runs.
Voltage Drop Limitations
The ampacity table tells you what size wire will prevent the insulation from melting; it does not tell you what size wire will deliver adequate voltage to the load. For branch circuits, the NEC recommends keeping voltage drop under 3%. On a 120V circuit, a 3% drop is 3.6 volts. If you run a 20A load on 12 AWG copper for 100 feet, the voltage drop will exceed 4%, causing motors to overheat and lights to dim. For a 100-foot, 20A run, you must upsize to 10 AWG wire, even though the breaker remains 20A.
Ambient Temperature Corrections
If your conduit runs through an attic that reaches 120°F (49°C) in the summer, the base ampacity drops. You must apply the temperature correction factors from the bottom of NEC Table 310.16. At 113°F to 122°F, you must multiply the 90°C ampacity by 0.82, significantly reducing the safe current limit before you even calculate bundling derating.
AWG Size Frequently Asked Questions
What AWG size wire do I need for a 50-amp breaker?
You need 6 AWG copper wire. According to the 75°C column of NEC Table 310.16, 6 AWG is rated for 65 amps, which safely covers a 50-amp load. However, if the run is exceptionally long (over 50 feet for a 240V EV charger) or if the wire is routed through a hot attic, upsizing to 4 AWG copper is standard practice to mitigate voltage drop and heat buildup.
Can I use 12 AWG wire on a 15-amp breaker?
Yes. NEC 240.4 allows you to use a larger wire on a smaller breaker. 12 AWG wire is rated for 20 amps, so protecting it with a 15-amp breaker is perfectly safe and code-compliant. Electricians often do this when they have leftover 12 AWG wire on a spool, or when they want the option to upgrade the breaker to 20 amps in the future without rewiring the circuit. You cannot, however, use 14 AWG wire on a 20-amp breaker.
What AWG size is required for a 100-amp subpanel feeder?
For a 100-amp subpanel feeder using copper wire, you need 3 AWG copper (rated 100A at 75°C). If you are using aluminum wire (such as SER cable), you must upsize by roughly two AWG steps, meaning you need 1 AWG aluminum (rated 100A at 75°C). Always ensure the subpanel's main lugs are rated for 75°C, which is standard for modern equipment.
How does aluminum AWG size compare to copper?
Aluminum has lower conductivity than copper, requiring a larger physical cross-section to carry the same current safely. As a general rule, aluminum wire must be two AWG sizes larger than copper for the same ampacity. For example, a 200-amp residential main service requires 2/0 AWG copper, but it requires 4/0 AWG aluminum. Because aluminum is significantly lighter and cheaper, it is the standard choice for utility drop lines, main service entrance cables (SER), and large feeder runs over 4 AWG.
