For standard residential branch circuits using copper wire with 60°C or 75°C insulation, the baseline wire AWG amps are: 14 AWG = 15A, 12 AWG = 20A, 10 AWG = 30A, 8 AWG = 40A, and 6 AWG = 55A. These values assume an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a raceway. If you are pulling wire today, match your breaker to the 60°C or 75°C column based on your terminal ratings, never the 90°C column.
How to Read the NEC 310.16 Ampacity Table
The definitive source for wire ampacity in the United States is NFPA 70: National Electrical Code (NEC) Table 310.16. When you look at this table, you will see three distinct temperature columns for both copper and aluminum: 60°C (140°F), 75°C (167°F), and 90°C (194°F). Here is how to determine which column applies to your installation:
- The 60°C Column: Use this for older installations, NM-B (Romex) cable assemblies (which are legally limited to the 60°C column for ampacity by NEC 334.80), and circuits rated 100A or less where the equipment terminal temperature rating is unknown or marked 60°C.
- The 75°C Column: Use this for most modern commercial and residential branch circuits and feeders. Modern breakers, lugs, and receptacles are typically rated for 75°C. THHN/THWN-2 wire in conduit can be sized using this column if the terminations are rated for it.
- The 90°C Column: Do not use this column for final breaker sizing. The 90°C column is strictly used as a starting point for calculating derating adjustments (like bundling or high ambient heat). Per NEC 110.14(C) terminal provisions, your final ampacity is bottlenecked by the lowest temperature rating in the circuit—usually the 75°C breaker lug.
The Small Conductor Rule (NEC 240.4(D)): Regardless of the insulation temperature rating, NEC 240.4(D) hard-caps the overcurrent protection for small copper conductors. 14 AWG is capped at 15A, 12 AWG at 20A, and 10 AWG at 30A, even if the 90°C column shows a higher number.
The Master Wire AWG Amps Reference Chart
Below is the complete data table for the most common residential and light-commercial wire sizes. Source: NEC 2023 Table 310.16, based on an ambient temperature of 30°C (86°F).
| AWG / kcmil | Copper 60°C (140°F) | Copper 75°C (167°F) | Copper 90°C (194°F) | Aluminum 75°C (167°F) |
|---|---|---|---|---|
| 14 | 15A * | 20A * | 25A * | — |
| 12 | 20A * | 25A * | 30A * | — |
| 10 | 30A * | 35A * | 40A * | — |
| 8 | 40A | 50A | 55A | 40A |
| 6 | 55A | 65A | 75A | 50A |
| 4 | 70A | 85A | 95A | 65A |
| 3 | 85A | 100A | 110A | 75A |
| 2 | 95A | 115A | 130A | 90A |
| 1 | 110A | 130A | 145A | 100A |
| 1/0 | 125A | 150A | 170A | 120A |
| 2/0 | 145A | 175A | 195A | 135A |
| 3/0 | 165A | 200A | 225A | 155A |
| 4/0 | 195A | 230A | 260A | 180A |
* Asterisk denotes sizes subject to the NEC 240.4(D) small conductor hard-cap rule for overcurrent protection.
Quick-Jump: Most Queried Residential Wire Sizes
Bookmark this section for the most common jobsite scenarios. These assume copper conductors and standard 75°C rated terminations.
- 14 AWG (15 Amps): General lighting circuits and low-draw bedroom receptacles. Never use on a 20A breaker.
- 12 AWG (20 Amps): Kitchen, bathroom, and outdoor receptacles. The standard for 20A small-appliance branch circuits.
- 10 AWG (30 Amps): Electric water heaters, window AC units, and standard clothes dryers (if the manufacturer specifies 30A).
- 8 AWG (40 Amps): Standard electric ranges and cooktops requiring a 40A circuit, or large HVAC condenser units.
- 6 AWG (55A Copper / 50A Aluminum): 50A hot tub spas, heavy-duty welder outlets (NEMA 14-50), and EV Level 2 chargers pulling 40A continuous.
- 4 AWG Copper / 2 AWG Aluminum (85A / 90A): 60A subpanel feeders (using the 83% continuous load rule for residential dwellings per NEC 310.12).
Derating: When the Base Value Drops
The numbers in the master table assume you have three or fewer current-carrying conductors in a conduit and an ambient temperature of 30°C (86°F). If you violate either assumption, you must derate the wire. Derating always starts from the 90°C column for THHN/THWN-2 wire, which is its sole practical purpose.
You are pulling four 12 AWG THHN wires (two hots, one neutral, one ground) through a single conduit to a multi-wire branch circuit. The ground does not count as a current-carrying conductor (CCC). You have 3 CCCs. No derating is required.
However, if you pull five 12 AWG THHN wires (two hots, two neutrals, one ground) for two separate 20A circuits, you now have 4 CCCs. Per NEC Table 310.15(C)(1), the adjustment factor for 4-6 conductors is 80%.
Math: 12 AWG 90°C base = 30A. 30A × 0.80 = 24A. Since 24A is still greater than your 20A breaker, 12 AWG is legally compliant. If you had 7-9 CCCs (70% factor), 30A × 0.70 = 21A. Still passes. But at 10-20 CCCs (50% factor), 30A × 0.50 = 15A. You would be forced to upsize to 10 AWG wire to protect it with a 20A breaker.
Decision Path: Picking Your Wire and Breaker
Use this decision-tree-table to terminate your planning phase and pick your exact materials. This assumes copper wire, standard residential loads, and 75°C terminals.
| If Your Load / Application Is... | Use This Wire (Copper) | Use This Breaker |
|---|---|---|
| Standard 15A lighting / bedroom receptacles | 14 AWG NM-B | 15A Single Pole |
| Kitchen / Bathroom / Garage 20A receptacles | 12 AWG NM-B | 20A Single Pole |
| 30A Electric Dryer or Water Heater | 10 AWG NM-B or THHN | 30A Double Pole |
| 40A Range / Cooktop | 8 AWG NM-B or THHN | 40A Double Pole |
| 50A EV Charger (40A continuous) or Hot Tub | 6 AWG THHN in conduit | 50A Double Pole |
| 60A Subpanel Feeder (Residential) | 4 AWG Copper or 2 AWG Aluminum SER | 60A Double Pole |
| 100A Subpanel Feeder (Residential) | 2 AWG Copper or 1/0 AWG Aluminum SER | 100A Double Pole |
What This Table Cannot Tell You
While the NEC 310.16 table is the law of the land for ampacity, it has blind spots that will ruin your installation if ignored:
- Voltage Drop: The table assumes a short run. If your wire run exceeds 100 feet, you must calculate voltage drop. A 3% drop is the standard maximum for branch circuits. For a 50A EV charger 150 feet away, 6 AWG will result in unacceptable voltage sag; you must upsize to 4 AWG copper purely for voltage drop mitigation, even though 6 AWG handles the thermal ampacity.
- Continuous vs. Non-Continuous Loads: If a load runs for 3 hours or more (like an EV charger or a hardwired heater), it is a 'continuous load'. NEC 210.20(A) requires you to size the overcurrent device at 125% of the continuous load. A 40A continuous EV charger requires a 50A breaker (40 × 1.25 = 50), and the wire must be sized to carry 50A.
- Aluminum Oxide and Torque: If you choose the aluminum column to save money on feeders, you must use an antioxidant compound (like Noalox) on the stripped wire ends and torque the lugs to the manufacturer's exact inch-pound specification using a calibrated torque screwdriver. Aluminum creeps and oxidizes; improper terminations cause fires.
When in doubt, buy the next size up in copper, use a torque screwdriver, and terminate on 75°C rated lugs. Your local Authority Having Jurisdiction (AHJ) has the final say on all interpretations of the NEC.
