The standard wire gauge table amperage for residential and commercial branch circuits relies on the 60°C or 75°C column of NFPA 70 (NEC) Table 310.16, depending on your equipment terminal ratings. For a standard 15A circuit, use 14 AWG copper; for 20A, use 12 AWG; for 30A, use 10 AWG.
How to read the table: The master chart is divided by conductor material (Copper vs. Aluminum) and then by insulation temperature rating (60°C, 75°C, and 90°C). The numbers in the cells represent the maximum allowable ampacity—the continuous current the wire can carry without degrading the insulation—assuming an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors bundled in a raceway. Always cross-reference the wire size with the breaker size; the breaker must protect the wire at its lowest rated ampacity.
Master Wire Gauge Table Amperage Chart (NEC 310.16)
Below is the data-dense reference chart for the most common building wire types (THHN, XHHW-2, NM-B). Use the quick-jump list to locate the most queried residential sizes, then consult the full table for exact ampacities.
- 15 Amps (Lighting/Receptacles): 14 AWG Copper (60°C column)
- 20 Amps (Kitchen/Bath/Laundry): 12 AWG Copper (60°C column)
- 30 Amps (Dryer/HVAC): 10 AWG Copper (60°C column)
- 50 Amps (Range/EV Charger): 6 AWG Copper (75°C column)
- 100 Amps (Subpanel Feeder): 3 AWG Copper or 1 AWG Aluminum (75°C column)
| AWG / kcmil Size | Copper 60°C (Amps) | Copper 75°C (Amps) | Copper 90°C (Amps) | Aluminum 75°C (Amps) |
|---|---|---|---|---|
| 14 AWG | 15 | 20 | 25 | - |
| 12 AWG | 20 | 25 | 30 | - |
| 10 AWG | 30 | 35 | 40 | - |
| 8 AWG | 40 | 50 | 55 | 40 |
| 6 AWG | 55 | 65 | 75 | 50 |
| 4 AWG | 70 | 85 | 95 | 65 |
| 3 AWG | 85 | 100 | 110 | 75 |
| 2 AWG | 95 | 115 | 130 | 90 |
| 1 AWG | 110 | 130 | 145 | 100 |
| 1/0 AWG | 125 | 150 | 170 | 120 |
| 2/0 AWG | 145 | 175 | 195 | 135 |
| 3/0 AWG | 165 | 200 | 225 | 155 |
| 4/0 AWG | 195 | 230 | 260 | 180 |
Which Temperature Column Applies to Your Installation?
The most common mistake DIYers and junior electricians make is sizing wire using the 90°C column because it allows for smaller, cheaper wire. In almost all residential and light-commercial applications, you cannot use the 90°C column for final ampacity sizing.
Here is the exact breakdown of which column governs your installation, dictated by NEC 110.14(C)(1):
The 60°C Column (The Default for Small Circuits)
For circuits rated 100 amps or less, or for conductors sized 14 AWG through 1 AWG, you must use the 60°C column unless the equipment (breaker, receptacle, lug) is explicitly marked otherwise. Standard residential breakers and receptacles are typically rated for 60°C terminations. Therefore, even if you pull 12 AWG THHN (which has 90°C insulation), your maximum allowable ampacity is capped at the 60°C rating of 20 Amps.
The 75°C Column (Modern Equipment and Larger Feeders)
Most modern breakers, panelboard lugs, and heavy-duty receptacles (like 14-50R range outlets) are rated for 75°C terminations. For circuits over 100 amps, or wire sizes larger than 1 AWG, the 75°C column becomes the default. This is why a 3 AWG copper wire can safely be placed on a 100A breaker (100A at 75°C), even though its 60°C rating is only 85A.
The 90°C Column (Strictly for Derating)
The 90°C column is almost exclusively used as a starting point for derating calculations. If your wire has 90°C insulation (like THHN or XHHW-2), you start with the 90°C ampacity, apply your bundling or temperature correction factors, and then compare the resulting derated number to the 60°C or 75°C termination limit. The final breaker size must protect the lowest number in that chain.
Derating Factors and What the Table Cannot Tell You
Table 310.16 assumes ideal conditions: an ambient air temperature of 30°C (86°F) and no more than three current-carrying conductors in a single raceway or cable. When real-world conditions deviate, the base values in the table must be modified.
How Derating Modifies the Base Value
When you bundle more than three current-carrying conductors in a conduit, the trapped heat reduces the wire's ability to dissipate thermal energy. NEC Table 310.15(C)(1) mandates adjustment factors.
Worked Numeric Example: You are pulling four current-carrying 12 AWG THHN wires through a single conduit to feed a multi-wire branch circuit and a separate 20A circuit.
- Base Value: 12 AWG THHN at 90°C is rated for 30 Amps.
- Adjustment Factor: 4 to 6 conductors require an 80% multiplier.
- Calculation: 30A × 0.80 = 24 Amps.
- Verification: 24 Amps is greater than your 20A load and breaker, so 12 AWG THHN is legally compliant. However, if you were using 12 AWG NM-B (Romex), which is limited to the 60°C column (20A base) regardless of derating, you would be forced to upsize to 10 AWG to handle the bundling heat.
What the Wire Gauge Table Cannot Tell You
Relying solely on an ampacity chart leaves three critical failure modes unaddressed:
- Voltage Drop Over Distance: NEC 310.16 dictates thermal safety (preventing fires), not electrical efficiency. A 10 AWG wire on a 30A breaker is thermally safe, but if that run is 150 feet to a detached garage, the voltage drop will exceed the recommended 3% threshold, causing motors to overheat and electronics to brownout. For runs over 100 feet, consult voltage drop calculators and typically upsize the wire by one or two AWG sizes.
- Conduit Fill Capacity: The table tells you the wire's electrical limit, not its physical footprint. NEC Chapter 9, Table 1 limits conduit fill to 40% for three or more wires. You cannot simply stuff ten 10 AWG THHN wires into a 1/2-inch EMT conduit just because the breaker sizing allows it; the physical jamming will damage the insulation during the pull.
- Short-Circuit Interrupting Capacity: Ampacity charts assume standard overload conditions. In the event of a dead short, the wire must withstand the magnetic and thermal forces until the breaker trips. This is governed by the breaker's AIC (Amps Interrupting Capacity) rating and the available fault current from the utility transformer, not the wire's continuous ampacity table.
