For standard residential branch circuits, the direct answer is simple: use 14 AWG for 15A, 12 AWG for 20A, and 10 AWG for 30A copper wire. These sizes are dictated by the 60°C column of NEC Table 310.16. However, once you move past basic receptacles into feeders, subpanels, or conduit runs, picking the right wire AWG requires understanding temperature columns, termination limits, and derating factors.
• 14 AWG: 15A Max (Lighting, general receptacles)
• 12 AWG: 20A Max (Kitchen/bath small appliance, garage)
• 10 AWG: 30A Max (Dryers, RV outlets, window ACs)
• 8 AWG: 40A Max (Cooktops, large EV chargers)
• 6 AWG: 55A/60A Max (Hot tubs, 60A subpanel feeders)
How to Read the NEC Wire AWG Table (Source & Columns)
The authoritative source for wire ampacity in the United States is NFPA 70 (National Electrical Code), specifically Table 310.16. When you open this table, you will see columns divided by conductor material (Copper vs. Aluminum) and insulation temperature rating (60°C, 75°C, and 90°C).
The most common mistake DIYers and junior apprentices make is looking at a spool of THHN wire (which is rated for 90°C), finding the 90°C column, and assuming a 12 AWG wire can safely carry 30 amps. This is a code violation and a fire hazard.
Which column applies to your installation? According to NEC 110.14(C), the ampacity of a circuit is limited by the temperature rating of its terminations (the lugs on your breakers, receptacles, and splices). Because most standard residential breakers and devices are rated for 75°C, and the NEC mandates a conservative baseline for circuits 100A or less, you must use the 60°C column to determine your maximum breaker size for almost all standard branch circuits. The 75°C and 90°C columns are primarily used for derating calculations and sizing large feeders over 100A where equipment is explicitly rated for 75°C terminations.
The Complete Copper Wire AWG Table (Ampacity & Breaker Sizing)
Below is the complete reference chart for copper conductors, cross-referenced with the maximum standard overcurrent protective device (breaker) size permitted under standard residential termination rules. Data is sourced from NEC Table 310.16 and standard breaker sizing per NEC 240.6.
| Wire Size (AWG/kcmil) | 60°C Ampacity (Branch Circuits) | 75°C Ampacity (Feeders/Terminations) | 90°C Ampacity (THHN/THWN Derating Base) | Max Standard Breaker Size* |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | 15A |
| 12 AWG | 20A | 25A | 30A | 20A |
| 10 AWG | 30A | 35A | 40A | 30A |
| 8 AWG | 40A | 50A | 55A | 40A |
| 6 AWG | 55A | 65A | 75A | 60A** |
| 4 AWG | 70A | 85A | 95A | 70A |
| 3 AWG | 85A | 100A | 115A | 100A |
| 2 AWG | 95A | 115A | 130A | 100A / 125A |
| 1 AWG | 110A | 130A | 145A | 125A |
| 1/0 AWG | 125A | 150A | 170A | 150A |
| 2/0 AWG | 145A | 175A | 195A | 175A |
| 3/0 AWG | 165A | 200A | 225A | 200A |
| 4/0 AWG | 195A | 230A | 260A | 225A / 250A |
* Per NEC 240.4(B), if the 60°C ampacity does not correspond to a standard breaker size, you may round up to the next standard size for circuits under 800A.
** 6 AWG at 60°C is 55A. The next standard breaker up is 60A, making 6 AWG the standard choice for 60A circuits.
Derating: When the Base Table Values Change
The ampacity values in the table above assume an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors bundled together in a raceway or cable. When you exceed these conditions, you must apply derating factors outlined in NEC 310.15.
How derating modifies the base value: Derating is always calculated using the 90°C column (for THHN/THWN-2 wire), even if your final breaker size is limited by the 60°C column. This is where the 90°C rating earns its keep.
You are pulling four current-carrying conductors (two hots, one neutral, one ground doesn't count) through a single conduit for a multi-wire branch circuit.
1. NEC Table 310.15(C)(1) dictates an 80% derating factor for 4-6 conductors.
2. You want to use 12 AWG THHN. The 90°C base ampacity is 30A.
3. 30A × 0.80 = 24A derated ampacity.
4. Since 24A is greater than your 20A breaker requirement, 12 AWG is perfectly legal and safe.
If you tried to use 14 AWG THHN (90°C base = 25A), the derated value would be 20A. Because you cannot round up for derated conductors in this specific scenario without violating the 15A breaker limit for 14 AWG terminations, you must stick to 12 AWG.
Wire Sizing Decision Tree: Pick Your Exact AWG
Use this decision path to terminate your sizing process with a concrete pick. Do not guess; follow the load requirements to the exact wire gauge.
| If Your Circuit Load / Application Is... | And The Run Is Under 50 Feet... | Then Your Exact Copper Wire Pick Is: |
|---|---|---|
| 15A Lighting or General Receptacles | Standard residential branch | 14 AWG (12 AWG recommended for voltage drop mitigation) |
| 20A Kitchen, Bath, or Garage Outlets | Standard residential branch | 12 AWG |
| 30A Dryer, RV Outlet, or Window AC | Standard residential branch | 10 AWG |
| 40A Cooktop or Level 2 EV Charger | Standard residential branch | 8 AWG |
| 50A Hot Tub or Range | Standard residential branch | 6 AWG |
| 60A Subpanel Feeder or EVSE | Terminations rated 75°C | 6 AWG (using 75°C column allowance) |
| 100A Subpanel Feeder | Terminations rated 75°C | 3 AWG Copper (or 1 AWG Aluminum) |
| 200A Main Service Entrance | Terminations rated 75°C | 2/0 AWG Copper (or 4/0 AWG Aluminum) |
What This Table Cannot Tell You (Voltage Drop & Local Code)
While the Copper Development Association and the NEC provide strict ampacity limits to prevent wires from melting, the wire AWG table completely ignores voltage drop. Ampacity tells you if the wire will catch fire; voltage drop tells you if your equipment will actually function.
NEC 310.15(B) includes an informational note recommending a maximum voltage drop of 3% for branch circuits and 5% for the total feeder-plus-branch system. If you are running a 20A circuit to a detached shed 120 feet away, 12 AWG copper will yield a voltage drop of roughly 3.8% at full load. The ampacity table says 12 AWG is legal, but your power tools will bog down and motors will overheat. In this scenario, you must upsize to 10 AWG to keep the drop under 3%, regardless of what the breaker sizing column dictates.
Furthermore, this table assumes standard installation methods. It cannot tell you if a 4 AWG wire will physically bend into the tight lug cavity of a specific brand of smart breaker, nor can it override your local Authority Having Jurisdiction (AHJ). Some municipalities mandate 12 AWG as the absolute minimum for all interior branch circuits, effectively banning 14 AWG entirely. Always verify local amendments before purchasing bulk wire.
