The ampacity of a conductor is not a single fixed number; it is dictated by the wire's AWG size, the metal used (copper vs. aluminum), and the temperature rating of its insulation. For standard residential and commercial branch circuits, a 12 AWG copper wire is rated for 20 amps, a 10 AWG for 30 amps, and a 6 AWG for 55 to 65 amps depending on the termination temperature. This guide provides the exact wire gauge chart amps based on the National Electrical Code (NEC) Table 310.16, eliminating the guesswork from your next wiring project.
How to Read the NEC 310.16 Wire Gauge Chart
Before pulling wire, you must understand which column of the ampacity table applies to your specific installation. The NEC Table 310.16 (formerly 310.15(B)(16)) divides ampacities into temperature columns: 60°C (140°F), 75°C (167°F), and 90°C (194°F).
The 60°C Rule for Small Conductors: Even if you buy 90°C THHN wire, NEC section 240.4(D) mandates that for conductors sized 14, 12, and 10 AWG, you must use the 60°C column for overcurrent protection limits. This means 14 AWG is capped at 15A, 12 AWG at 20A, and 10 AWG at 30A, regardless of the 90°C column showing higher numbers.
For larger wires (8 AWG and above), you look at the temperature rating of the terminations (the lugs on your breakers, panels, and receptacles). Most modern residential breakers and panels are rated for 75°C, allowing you to use the 75°C column. The 90°C column is almost exclusively used as the starting baseline for calculating derating factors, which we will cover below. For a deeper dive into termination ratings, the Electrical Training Alliance provides excellent code-cycle updates on lug temperature assumptions.
The Master Wire Gauge Chart Amps Table
The following table reproduces the core values from NEC Table 310.16 for standard solid and stranded conductors in raceway or cable (like NM-B or THHN in conduit) at an ambient temperature of 30°C (86°F).
| AWG / kcmil Size | Copper 60°C (Amps) | Copper 75°C (Amps) | Copper 90°C (Amps) | Aluminum 75°C (Amps) | Aluminum 90°C (Amps) |
|---|---|---|---|---|---|
| 14 | 15 | 20 | 25 | -- | -- |
| 12 | 20 | 25 | 30 | -- | -- |
| 10 | 30 | 35 | 40 | -- | -- |
| 8 | 40 | 50 | 55 | 40 | 45 |
| 6 | 55 | 65 | 75 | 50 | 60 |
| 4 | 70 | 85 | 95 | 65 | 75 |
| 3 | 85 | 100 | 115 | 75 | 85 |
| 2 | 95 | 115 | 130 | 90 | 100 |
| 1 | 110 | 130 | 145 | 100 | 115 |
| 1/0 | 125 | 150 | 170 | 120 | 135 |
| 2/0 | 145 | 175 | 195 | 135 | 150 |
| 3/0 | 165 | 200 | 225 | 155 | 175 |
| 4/0 | 195 | 230 | 260 | 180 | 205 |
Bookmark-Friendly Quick Jumps for Common Circuits
If you are in the middle of a rough-in and just need the standard residential answer, use these quick-jump rules. These assume standard 75°C rated panels and copper conductors unless noted.
- 15A Lighting/Receptacle Circuit: 14 AWG Copper (60°C column limit per 240.4(D)). Breaker: 15A.
- 20A Kitchen/Bath Receptacle Circuit: 12 AWG Copper (60°C column limit). Breaker: 20A.
- 30A Dryer or RV Receptacle: 10 AWG Copper (60°C column limit). Breaker: 30A.
- 40A EV Charger or Range: 8 AWG Copper (75°C column = 50A). Breaker: 40A.
- 50A Hot Tub or Welder: 6 AWG Copper (75°C column = 65A). Breaker: 50A.
- 100A Subpanel Feeder: 3 AWG Copper or 1 AWG Aluminum (75°C column). Breaker: 100A.
- 200A Residential Service: 2/0 AWG Copper or 4/0 AWG Aluminum. Note: NEC 310.12 specifically permits 4/0 Aluminum for 200A residential services, even though the 75°C table lists it at 180A.
Derating: When the Chart Value Shrinks
The base ampacities in the master table assume two things: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a single raceway. When these conditions change, you must apply derating factors to the 90°C column (for copper THHN/THWN-2) to find your true allowable ampacity.
1. Ambient Temperature Derating: If your conduit runs across a hot attic or an outdoor roof where the ambient temperature reaches 110°F (43°C), you must multiply the 90°C ampacity by 0.87. For example, a 10 AWG THHN wire has a 90°C rating of 40A. At 110°F, 40A x 0.87 = 34.8A. Because 34.8A is still above the 30A limit set by 240.4(D), you can still use it on a 30A breaker.
2. Bundling (Conduit Fill) Derating: When you pull more than three current-carrying conductors in one conduit, they heat each other up. If you have 4 to 6 conductors, multiply the 90°C ampacity by 80%. If you have 7 to 9 conductors, multiply by 70%.
Worked Example: You are pulling two 120V circuits (2 hots, 2 neutrals = 4 current-carrying conductors) plus a ground wire in a single EMT conduit. You want to use 12 AWG THHN for 20A breakers. The 90°C column for 12 AWG is 30A. Applying the 80% bundling factor: 30A x 0.80 = 24A. Because 24A is greater than your 20A breaker size, 12 AWG THHN is perfectly legal and safe. If you added a third circuit (6 current-carrying wires), 30A x 0.80 = 24A, which still passes. But if you pulled four circuits (8 wires), the factor drops to 70%: 30A x 0.70 = 21A. This is dangerously close to the 20A continuous load limit, requiring an upgrade to 10 AWG wire.
Decision Tree: Pick Your Exact Wire and Breaker
Use this decision matrix to lock in your materials. Follow the path that matches your load to arrive at a concrete, code-compliant pick.
| Installation Scenario | Condition / Constraint | Concrete Pick (Wire & Breaker) |
|---|---|---|
| Standard 120V Wall Receptacles | Max 1.5A per outlet, general use | 14 AWG NM-B on a 15A AFCI/GFCI Breaker |
| Kitchen Small Appliance Branch | High draw (microwave, toaster) | 12 AWG NM-B on a 20A GFCI Breaker |
| Hardwired EV Charger (40A continuous) | NEC requires 125% sizing for continuous loads (40 x 1.25 = 50A) | 6 AWG THHN in conduit on a 50A Breaker |
| 100A Detached Garage Subpanel | Underground PVC conduit, 75°C lugs | 1 AWG Aluminum XHHW-2 on a 100A Breaker |
| 200A Main Service Entrance | Overhead mast or underground SER cable | 4/0 AWG Aluminum SE-R on a 200A Main Breaker |
What This Table Cannot Tell You
While the wire gauge chart amps table is the absolute authority on thermal limits and overcurrent protection, it has three blind spots that you must calculate separately:
- Voltage Drop: NEC Table 310.16 does not account for distance. If you are running a 12 AWG wire 150 feet to a shed on a 20A circuit, the wire will not melt, but the voltage at the shed will drop below 114V, causing motors to overheat and lights to dim. For runs over 100 feet, always calculate voltage drop and typically upsize the wire by one or two AWG sizes.
- Physical Lug Fit: The table assumes the wire physically fits into the breaker or panel lug. Many standard 20A and 30A residential breakers are not physically rated to accept stranded wire larger than 8 AWG or solid wire larger than 6 AWG. Always check the breaker manufacturer's datasheet for maximum wire size before buying.
- Short-Circuit Let-Through Current: Ampacity dictates how much continuous current the wire can carry without the insulation melting. It does not tell you how the wire behaves during a 10,000-amp dead short. That is the domain of the breaker's interrupting rating (AIC) and the wire's short-circuit withstand rating, which is why you must never install a breaker larger than the wire's ampacity (with specific exceptions like motor starting surges).
