The AWG (American Wire Gauge) system standardizes wire diameter and current-carrying capacity (ampacity) across North America. The lower the AWG number, the thicker the conductor and the higher the safe current limit. For any US-based residential or commercial installation, the ultimate authority is the National Electrical Code (NEC), specifically Table 310.16.
How to read this table: The chart below assumes solid or stranded copper wire, an ambient temperature of 30°C (86°F), and no more than three current-carrying conductors bundled in a single raceway or cable. The temperature columns (60°C, 75°C, 90°C) correspond to the thermal rating of the wire's insulation (e.g., TW, THWN, THHN). Always cross-reference these values with your local AHJ (Authority Having Jurisdiction), as local amendments can override baseline NEC guidance.
The Complete AWG American Wire Gauge Table (NEC 310.16)
Quick-jump to the most queried residential sizes: 14 AWG | 12 AWG | 10 AWG | 6 AWG | 4 AWG | 2 AWG
| AWG Size | 60°C (140°F) TW, UF |
75°C (167°F) RHW, THHW, XHHW |
90°C (194°F) THHN, THWN-2 |
Max Standard Breaker |
|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | 15A |
| 12 AWG | 20A | 25A | 30A | 20A |
| 10 AWG | 30A | 35A | 40A | 30A |
| 8 AWG | 40A | 50A | 55A | 40A / 50A* |
| 6 AWG | 55A | 65A | 75A | 60A |
| 4 AWG | 70A | 85A | 95A | 80A |
| 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 |
*Note: 8 AWG copper is limited to 40A under the 60°C column, but NEC 240.4(D) requires specific overcurrent protection limits for small conductors. Always verify 8 AWG usage against 240.4(D) before using a 50A breaker.
Which Column Applies and How Derating Modifies Base Values
The most common mistake DIYers and junior apprentices make is looking at the 90°C column for THHN wire and sizing the breaker to that number. You almost never use the 90°C column for final breaker sizing.
Under NEC 110.14(C), the ampacity of a circuit is limited by the lowest temperature rating of any connected component. Most standard residential breakers, receptacles, and wire nuts are rated for 75°C. Furthermore, for circuits rated 100A or less (or using 14 through 1 AWG wire), NEC rules default to the 60°C column unless the equipment is explicitly marked otherwise. Therefore, a 12 AWG THHN wire (90°C insulation) in a standard residential outlet circuit is still legally limited to the 60°C rating of 20A.
The 90°C column's primary purpose is to give you a higher baseline mathematically before applying environmental penalty factors (derating).
How Derating Rows Modify the Base Value
When you pull more than three current-carrying conductors through a single conduit, the trapped heat forces you to reduce (derate) the wire's ampacity per NEC Table 310.15(C)(1). Here is the exact workflow:
- Start with the 90°C column. Example: You are pulling four 12 AWG THHN wires (two hots, two neutrals for two separate 120V circuits) through one EMT conduit.
- Find the derating factor. For 4 to 6 current-carrying conductors, the multiplier is 80%.
- Do the math. 12 AWG at 90°C is 30A. 30A × 0.80 = 24A.
- Compare to the termination limit. Your derated ampacity (24A) is higher than the 60°C termination limit (20A). Therefore, you can still safely terminate this wire on a standard 20A breaker.
If you had pulled 7 to 9 conductors (70% derating), the math would be 30A × 0.70 = 21A. Still safe for a 20A breaker. But if you pulled 10 to 20 conductors (50% derating), 30A × 0.50 = 15A. You would be forced to upsize to 10 AWG wire to maintain a 20A circuit.
What the AWG Table Cannot Tell You
While the AWG American wire gauge table is the gold standard for thermal safety (preventing wire fires), it is blind to several critical jobsite variables:
- Voltage Drop: The table assumes the wire can handle the current thermally, but it does not account for distance. Pushing 30A through 10 AWG copper is perfectly legal thermally, but if that run is 150 feet long on a 240V circuit, you will experience a ~7V drop (nearly 3%). For long feeder runs to subpanels or detached garages, you must calculate voltage drop and typically upsize the wire by one or two AWG steps to keep the drop under 3%.
- Ambient Temperature Corrections: The table assumes a baseline ambient temperature of 30°C (86°F). If you are routing wire through a hot attic space that reaches 45°C (113°F), you must apply an ambient temperature correction factor from NEC Table 310.15(B)(1), which will reduce your allowable ampacity.
- Aluminum vs. Copper: The table provided above is strictly for copper. Aluminum wire has a lower conductivity and requires a larger physical diameter to carry the same current. If you are using aluminum (common for 2/0 and 4/0 service entrance feeders), you must use the aluminum section of NEC 310.16, which yields significantly lower ampacities for the same AWG size.
AWG American Wire Gauge Table FAQ
What is the difference between AWG and kcmil in the wire gauge table?
AWG (American Wire Gauge) is used for smaller conductors, typically ranging from 14 AWG up to 4/0 AWG. Once wire thickness exceeds 4/0, the industry switches to kcmil (thousands of circular mils), such as 250 kcmil or 350 kcmil. A circular mil is a unit of cross-sectional area. You will generally only encounter kcmil in heavy commercial work or massive residential service entrances (e.g., 320A continuous meter mains).
Why does my 10 AWG wire have a 40A rating in the 90°C column but I can only use a 30A breaker?
This is dictated by NEC 110.14(C) and NEC 240.4(D). Even though THHN insulation can physically withstand 40A without melting (the 90°C rating), the brass terminals inside your breaker and receptacles are usually only rated for 60°C or 75°C. Furthermore, NEC 240.4(D) specifically caps the overcurrent protection for 10 AWG copper at 30A to protect the downstream terminals from thermal degradation, regardless of the wire's insulation rating.
Does the AWG American wire gauge table apply to automotive or marine DC wiring?
No. The NEC and Table 310.16 are designed for AC building wiring. Automotive (SAE J1128) and marine (ABYC E-11) DC systems operate under entirely different standards. DC systems often use finer-stranded wire for flexibility and require different ampacity calculations due to the continuous nature of DC loads and the vibration/moisture environments of vehicles and boats. Always use a dedicated marine or automotive wire sizing chart for 12V/24V DC applications.
How do I calculate wire size for a 60A subpanel using the AWG table?
For a standard 60A subpanel feeder using copper, look at the 75°C column (assuming your panel lugs are rated 75°C, which most modern ones are). You need a wire rated for at least 60A. According to the table, 6 AWG copper is rated 65A at 75°C, making it the minimum legal size. However, if the run exceeds 75 feet, you should calculate voltage drop and likely upsize to 4 AWG copper to ensure the panel receives adequate voltage under heavy load.
