For standard residential copper branch circuits, match 14 AWG to a 15-amp breaker, 12 AWG to 20 amps, 10 AWG to 30 amps, 8 AWG to 40 amps, and 6 AWG to 55 amps (typically protected at 50A or 60A). These baseline pairings assume copper conductors, a maximum of three current-carrying wires in a raceway, and an ambient temperature of 30°C (86°F). If your installation deviates from these baseline conditions, you must apply derating factors or upsize your conductors to prevent insulation meltdown and nuisance tripping.
How to Read This Wire Gauge and Amperage Chart
Before pulling wire, you need to understand how to read the grid. The rows represent the American Wire Gauge (AWG) size, where a smaller number indicates a thicker wire with higher current capacity. The columns are split by conductor material (Copper vs. Aluminum) and insulation temperature rating (60°C, 75°C, and 90°C).
According to NEC 110.14(C), for circuits rated 100 amps or less, or for wire sizes 14 AWG through 1 AWG, you must default to the 60°C column for ampacity sizing unless the equipment terminals are explicitly marked for 75°C. Even if you pull 90°C THHN wire through your conduit, the termination point at the breaker or receptacle is the thermal bottleneck. Most modern breakers and commercial receptacles are 75°C rated, but standard residential NM-B (Romex) cable is strictly limited to the 60°C column regardless of the breaker terminal rating.
The Master AWG, Ampacity, and Breaker Sizing Table
The data below is sourced directly from NEC Table 310.16 (allowable ampacities for insulated conductors rated up to 2000 volts). Use the quick-jump links to navigate to the most queried residential circuit sizes.
- Quick Jump: 15A (14 AWG) | 20A (12 AWG) | 30A (10 AWG) | 50A (6 AWG)
| AWG Size | Copper 60°C (NM-B) | Copper 75°C (THHN) | Aluminum 75°C | Max Standard Breaker |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | N/A | 15A |
| 12 AWG | 20A | 25A | 15A | 20A |
| 10 AWG | 30A | 35A | 30A | 30A |
| 8 AWG | 40A | 50A | 40A | 40A / 50A* |
| 6 AWG | 55A | 65A | 50A | 60A |
| 4 AWG | 70A | 85A | 65A | 70A / 80A* |
| 3 AWG | 85A | 100A | 75A | 90A / 100A* |
| 2 AWG | 95A | 115A | 90A | 100A / 110A* |
| 1 AWG | 110A | 130A | 100A | 125A |
| 1/0 AWG | 125A | 150A | 120A | 150A |
| 2/0 AWG | 145A | 175A | 135A | 175A |
| 3/0 AWG | 165A | 200A | 155A | 200A |
| 4/0 AWG | 195A | 230A | 180A | 225A |
*Breaker sizes marked with an asterisk utilize the NEC 240.4(B) "next size up" rule, allowing the overcurrent device to exceed the exact wire ampacity if the exact ampacity does not correspond to a standard breaker size listed in NEC 240.6.
When Base Ampacity Fails: Derating and Installation Variables
The chart above provides the base ampacity. In the real world, installation conditions frequently strip away that capacity. Here is how derating rows modify the base value, and what the table cannot tell you.
Conductor Bundling Derating
Under NEC 310.15(C)(1), when you pull more than three current-carrying conductors in a single raceway or conduit, the wires heat each other up. You must apply a derating multiplier to the 90°C column (not the 60°C column) to find your adjusted ampacity.
- 4 to 6 conductors: Multiply base 90°C ampacity by 80%.
- 7 to 9 conductors: Multiply by 70%.
- 10 to 20 conductors: Multiply by 50%.
Worked Example: You are pulling 12 AWG THHN for a 20-amp circuit, but you have 6 current-carrying conductors in the conduit. The 90°C ampacity for 12 AWG is 30A. Applying the 80% derating factor (30A × 0.80) yields 24A. Because 24A is still greater than your 20A load and breaker size, 12 AWG is legally compliant. However, if you had 10 conductors (50% derating), 30A × 0.50 = 15A. You would be forced to upsize to 10 AWG wire to safely protect a 20A circuit.
What the Table Cannot Tell You
Ampacity charts only measure thermal limits—they tell you the point at which the insulation will melt. They do not account for voltage drop. If you run 12 AWG wire 150 feet to a 15-amp shop vacuum, the wire won't overheat, but the voltage at the receptacle might drop below 110V, causing the motor to stall and burn out. For any run exceeding 100 feet, use a voltage drop calculator and upsize your wire to maintain a maximum 3% voltage drop. Furthermore, the table assumes an ambient temperature of 30°C (86°F). If your conduit runs through an attic that reaches 120°F in the summer, you must apply ambient temperature correction factors from NEC Table 310.15(B)(1).
Wire Gauge and Amperage Chart FAQ
What size wire do I need for a 50 amp breaker?
For a standard 50-amp circuit (like an EV charger or welder outlet), you need 6 AWG copper wire. Looking at the 60°C column, 6 AWG copper is rated for 55 amps, which safely covers the 50-amp load. If you are using aluminum wire (such as SER cable for a subpanel feeder), you must step up to 4 AWG aluminum, which is rated for 65 amps at 75°C. Never use 8 AWG copper for a 50-amp breaker; while its 75°C rating is 50A, NEC 110.14(C) terminal rules and standard residential NM-B limitations restrict 8 AWG to 40 amps in most branch circuit scenarios.
Can I use 14 AWG wire on a 20 amp circuit?
No. NEC 240.4(D) explicitly locks 14 AWG copper to a maximum 15-amp overcurrent device, regardless of the wire's theoretical thermal limits or the insulation type. Even if you are only powering a single 12-amp device, the breaker protecting the 14 AWG wire cannot exceed 15 amps. If your breaker is 20 amps, you must use a minimum of 12 AWG copper wire. Mixing 14 AWG wire into a 20-amp circuit is a leading cause of residential electrical fires, as the breaker will not trip before the 14 AWG wire begins to overheat under a sustained 18-amp load.
How does voltage drop change the wire gauge and amperage chart values?
Voltage drop does not change the ampacity (thermal safety) of the wire, but it dictates the practical wire size you must buy. The NEC recommends a maximum 3% voltage drop on branch circuits and 5% total from the service entrance to the furthest outlet. For example, pulling 10 AWG copper on a 30-amp circuit 200 feet away will result in roughly a 7% voltage drop at full load. To fix this, you must ignore the ampacity chart's minimums and upsize to 6 AWG or even 4 AWG copper purely to push the voltage back up to acceptable levels. Always calculate voltage drop for runs over 75 feet on 120V circuits, or over 150 feet on 240V circuits.
