For standard residential branch circuits, use 14 AWG copper for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, and 6 AWG for 55A. These baseline values assume copper conductors evaluated in the 60°C ampacity column, which is the legal default for most home wiring under 100 amps. If you are pulling individual THHN wires in conduit for a subpanel, you can often use the 75°C column for larger feeders, but the 60°C column remains the anchor point for standard NM-B (Romex) cable.
How to Read the AWG Amperage Chart
Before you cut any wire, you must understand how to read the columns. The master chart below is based on NEC Table 310.16 (formerly 310.15(B)(16)), the definitive standard for conductor ampacity in the United States. The table is divided by conductor material (Copper vs. Aluminum) and temperature rating (60°C, 75°C, and 90°C).
Even if you buy THHN wire with 90°C insulation, NEC 110.14(C) and 334.80 dictate that you must size your overcurrent protection based on the lowest temperature rating of any connected component. Since standard residential receptacles, switches, and NM-B cable jackets are rated for 60°C, you must use the 60°C column for almost all branch circuits under 100A. You only use the 75°C or 90°C columns for derating calculations or specific high-temp industrial terminations.
The Master AWG Amperage Chart (NEC Table 310.16)
This table reflects the allowable ampacities for insulated conductors rated up to 2000 volts, based on an ambient temperature of 30°C (86°F). Source standard: NFPA 70 National Electrical Code (NEC).
| AWG / kcmil Size | Copper 60°C (140°F) | Copper 75°C (167°F) | Copper 90°C (194°F) | Aluminum 75°C (167°F) |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | -- |
| 12 AWG | 20A | 25A | 30A | -- |
| 10 AWG | 30A | 35A | 40A | -- |
| 8 AWG | 40A | 50A | 55A | 40A |
| 6 AWG | 55A | 65A | 75A | 50A |
| 4 AWG | 70A | 85A | 95A | 65A |
| 3 AWG | 85A | 100A | 110A | 75A |
| 2 AWG | 95A | 115A | 130A | 90A |
| 1 AWG | 110A | 130A | 145A | 100A |
| 1/0 AWG | 125A | 150A | 170A | 120A |
| 2/0 AWG | 145A | 175A | 195A | 135A |
| 3/0 AWG | 165A | 200A | 225A | 155A |
| 4/0 AWG | 195A | 230A | 260A | 180A |
Quick-Jump: Most Queried Wire Sizes for Home Wiring
Bookmark this section for the most common residential circuit sizes. These assume standard copper NM-B or THHN in conduit, terminated on 60°C/75°C rated equipment.
- 15-Amp Lighting/Receptacle Circuit: 14 AWG Copper. (Breaker: 15A single-pole).
- 20-Amp Kitchen/Bathroom/Basement Circuit: 12 AWG Copper. (Breaker: 20A single-pole).
- 30-Amp Dryer/Water Heater/AC Circuit: 10 AWG Copper. (Breaker: 30A double-pole).
- 40-Amp Range/Cooktop Circuit: 8 AWG Copper. (Breaker: 40A double-pole).
- 50-Amp EV Charger/Hot Tub Circuit: 6 AWG Copper. (Breaker: 50A double-pole. Note: 6 AWG at 60°C is rated 55A, which safely covers a 50A continuous load requirement when sized at 125%).
- 100-Amp Subpanel Feeder: 3 AWG Copper or 1 AWG Aluminum. (Breaker: 100A double-pole).
Derating: When the Chart Lies
The ampacities in the master chart assume two things: an ambient temperature of 30°C (86°F), and no more than three current-carrying conductors bundled together. When you violate either condition, the base ampacity drops. This is where the 90°C column becomes useful—not for sizing the breaker, but for calculating derating.
Worked Example: You are pulling four 12 AWG THHN copper wires (two hots, two neutrals for two separate 20A circuits) through a single EMT conduit in a 30°C attic.
1. Base ampacity at 90°C for 12 AWG is 30A.
2. NEC Table 310.15(C)(1) dictates an 80% derating factor for 4-6 conductors.
3. 30A × 0.80 = 24A.
4. Because 24A is still greater than the 20A breaker limit (and greater than the 60°C column baseline of 20A), the 12 AWG wire is legally compliant. However, if you added two more wires (6 total, 50% derating), the ampacity would drop to 15A, forcing you to upsize to 10 AWG wire to maintain a 20A circuit.
Decision Tree: Pick Your Wire and Breaker
Use this matrix to terminate your planning phase and make a concrete purchase. Calculate your maximum continuous load, multiply by 1.25 (125% rule for continuous loads running 3+ hours), and match it below.
| Calculated Load (w/ 125% buffer) | Required Wire Size (Copper) | Concrete Breaker Pick | Typical Application |
|---|---|---|---|
| Up to 12A | 14 AWG NM-B | 15A (e.g., Square D QO115) | Bedroom lighting & general receptacles |
| 13A to 16A | 12 AWG NM-B | 20A (e.g., Square D QO120) | Kitchen small appliance, garage tools |
| 17A to 24A | 10 AWG THHN/NM-B | 30A (e.g., Square D QO230) | Standard electric dryer, window AC units |
| 25A to 32A | 8 AWG THHN/NM-B | 40A (e.g., Square D QO240) | Electric range, large shop welder |
| 33A to 40A | 6 AWG THHN/NM-B | 50A (e.g., Square D QO250) | Level 2 EV charger, spa panel |
| 41A to 55A | 4 AWG THHN in conduit | 60A (e.g., Square D QO260) | Heavy machinery, large subpanel feeder |
What This Chart Cannot Tell You
While the Copper Development Association and the NEC provide exhaustive thermal limits, an amperage chart is blind to three critical real-world factors:
- Voltage Drop Over Distance: The chart assumes the wire is short enough that resistance doesn't cause a meaningful voltage drop. If your EV charger is 150 feet from the panel, 6 AWG copper will suffer a voltage drop exceeding the recommended 3% threshold. You must upsize to 4 AWG or 3 AWG strictly to maintain voltage, even though 6 AWG handles the thermal amperage perfectly.
- Physical Lug Fit: A 4/0 AWG aluminum feeder might be the exact mathematical pick for a 200A service, but many older 200A main breaker lugs are not physically rated to accept wires larger than 2/0 AWG. Always check the terminal lug specifications on the panel label before buying large-gauge wire.
- Short-Circuit Let-Through Energy: Ampacity measures sustained thermal capacity. It does not tell you how the wire will survive a 10,000-amp short circuit event before the breaker trips. Proper breaker coordination and available fault current calculations are required for commercial and industrial panels.
Keep this chart in your phone's browser bookmarks. When you are standing in the aisle of the electrical supply house, referencing the 60°C copper column will keep your installation safe, legal, and inspection-ready.
