For standard 120V/240V residential branch circuits, the baseline AWG gauge picks are: 14 AWG for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, and 6 AWG for 55A. These values assume copper conductors and standard 60°C termination limits. If you are running aluminum feeder cable, you must step up two sizes (e.g., 2 AWG Aluminum for a 100A subpanel).
How to Read the NEC AWG Gauge Table
The National Electrical Code (NEC) publishes ampacity limits in Table 310.16. To use this table correctly, you must understand which temperature column applies to your installation. Wire insulation (like THHN) is often rated for 90°C, but your breaker lugs and receptacle terminals are typically only rated for 75°C or 60°C.
Per NEC 110.14(C), for circuits rated 100 amps or less, you must size the wire using the 60°C column unless the equipment is explicitly marked for 75°C terminations. Furthermore, if you are using standard NM-B (Romex) cable, NEC 334.80 mandates that you must use the 60°C column regardless of the fact that the internal THHN conductors are technically rated for 90°C.
Complete AWG Gauge and Ampacity Reference Chart
The following spec-sheet-table provides the exact ampacities for copper and aluminum conductors. Bookmark this page and use your browser's find function (Ctrl+F) to jump to the most queried residential sizes: 14, 12, 10, and 6 AWG.
Source: NEC Table 310.16 (formerly 310.15(B)(16)). Values assume not more than three current-carrying conductors in a raceway, 30°C ambient temperature.
| AWG Gauge | Copper 60°C (NM-B) | Copper 75°C (THWN) | Copper 90°C (THHN) | Aluminum 75°C | Max Standard Breaker (Cu 60°C) |
|---|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | N/A | 15A |
| 12 AWG | 20A | 25A | 30A | N/A | 20A |
| 10 AWG | 30A | 35A | 40A | N/A | 30A |
| 8 AWG | 40A | 50A | 55A | 40A | 40A |
| 6 AWG | 55A | 65A | 75A | 50A | 60A* |
| 4 AWG | 70A | 85A | 95A | 65A | 70A |
| 3 AWG | 85A | 100A | 110A | 75A | 90A |
| 2 AWG | 95A | 115A | 130A | 90A | 100A* |
| 1 AWG | 110A | 130A | 145A | 100A | 110A |
| 1/0 AWG | 125A | 150A | 170A | 120A | 125A |
| 2/0 AWG | 145A | 175A | 195A | 135A | 150A |
| 3/0 AWG | 165A | 200A | 225A | 155A | 175A |
| 4/0 AWG | 195A | 230A | 260A | 180A | 200A |
*Note: NEC 240.4(D) places special restrictions on small conductors. 6 AWG copper is strictly limited to a 60A breaker, and 2 AWG copper is limited to a 100A breaker for standard residential overcurrent protection, even if the 75°C column shows a higher theoretical ampacity.
Derating: When Your Base Ampacity Drops
The table above assumes ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors (CCCs) in a single conduit. When you bundle wires or run them through hot attics, you must apply derating factors per NEC 310.15(C)(1) and 310.15(B)(1).
Worked Numeric Example: You are pulling four 12 AWG THHN circuits (8 CCCs total) through a single conduit in a garage where the ambient temperature reaches 40°C (104°F).
- Base Ampacity: 12 AWG THHN in the 90°C column is 30A.
- Ambient Correction (40°C): The 90°C column correction factor is 0.91. (30A × 0.91 = 27.3A).
- Bundling Adjustment (8 CCCs): The adjustment factor for 7-9 conductors is 70%. (27.3A × 0.70 = 19.11A).
- Final Result: Your derated ampacity is 19.11A. Because this is below the 20A threshold, you must upsize to 10 AWG THHN to safely protect these circuits with standard 20A breakers.
AWG Gauge Decision Tree: Pick Your Wire
Stop guessing. Use this decision-tree-table to select the exact wire size and breaker combination for standard residential loads. This assumes standard copper NM-B or THHN in conduit, with standard 60°C/75°C terminations.
| Circuit Application | Continuous Load Limit (80%) | Required Breaker | Exact AWG Pick (Copper) | Exact AWG Pick (Aluminum Feeder) |
|---|---|---|---|---|
| General Lighting & Receptacles | 12A | 15A | 14 AWG | N/A |
| Kitchen/Bath Small Appliance | 16A | 20A | 12 AWG | N/A |
| Electric Dryer / RV Outlet | 24A | 30A | 10 AWG | 8 AWG |
| EV Charger (Level 2, 32A) | 32A | 40A | 8 AWG | 6 AWG |
| Electric Range / Cooktop | 40A | 50A | 6 AWG | 4 AWG |
| Hot Tub / Spa (Standard) | 40A | 50A | 6 AWG | 4 AWG |
| 100A Subpanel Feeder | 80A | 100A | 4 AWG (SER) / 3 AWG (THHN) | 2 AWG (SER) |
| 200A Main Service Feeder | 160A | 200A | 2/0 AWG (SER) | 4/0 AWG (SER) |
What This AWG Gauge Table Cannot Tell You
Ampacity charts only tell you the point at which the wire's insulation will melt or degrade. They do not account for voltage drop. According to the Copper Development Association and NEC informational notes, branch circuits should be designed to keep voltage drop under 3%, and the total feeder-plus-branch drop under 5%.
If you are running a 12 AWG copper wire 120 feet from the panel to a 15A window AC unit, the wire will not overheat (it is protected by a 15A breaker). However, the voltage drop will be approximately 4.3%. The AC compressor will struggle to start, draw excess current, and potentially burn out. In this scenario, the ampacity table says 12 AWG is fine, but physics dictates you must bump up to 10 AWG to maintain voltage stability over that distance.
The Final Rule: Always size your wire first to satisfy the NEC ampacity and termination temperature tables, then verify your run length against a voltage drop calculator. If the voltage drop exceeds 3% at maximum load, increase your AWG gauge by one size and re-verify. Never reduce wire size below the minimums listed in the chart above, regardless of how short the run is.
