When sizing conductors for residential or commercial circuits, the AWG wire amperage table is your foundational reference. In the United States, this data is governed by NEC Table 310.16 (formerly 310.15(B)(16)). For standard residential branch circuits using copper wire, the baseline ampacities are: 14 AWG = 15A, 12 AWG = 20A, 10 AWG = 30A, 8 AWG = 40A, and 6 AWG = 55A (at the 60°C column).
However, simply matching a breaker size to a single column in this table is a common jobsite mistake. The correct ampacity depends on your wire insulation type, the temperature rating of your termination points, and conduit fill derating. Below is the complete reference chart, followed by the exact rules for applying it to your installation.
How to Read the AWG Wire Amperage Table
The most critical skill in using the AWG wire amperage table is knowing which column applies to your installation. The table is divided by conductor material (Copper vs. Aluminum) and temperature rating (60°C, 75°C, and 90°C).
To select the correct column, you must follow NEC Section 110.14(C), which dictates terminal temperature limitations:
- The 60°C (140°F) Column: You must use this column for circuits rated 100 amps or less, or for wire sizes 14 AWG through 1 AWG, unless the equipment (breaker, receptacle, lug) is explicitly tested and marked for 75°C. Most standard NM-B (Romex) cable is inherently limited to 60°C ampacity regardless of the wire's internal insulation.
- The 75°C (167°F) Column: Used for circuits over 100A, or wire sizes larger than 1 AWG. It is also used for smaller wires if both the wire insulation (like THHN) and the equipment terminals are rated and marked for 75°C. Most modern commercial breakers and panel lugs carry a 75°C rating.
- The 90°C (194°F) Column: This column is almost never used for final breaker sizing. It is strictly used as the starting baseline for derating calculations (adjusting for ambient heat or conduit fill) before applying the terminal temperature limits.
Complete NEC Table 310.16 Ampacity Chart
The following table provides the allowable ampacities for insulated conductors rated up to 2000 volts, in an ambient temperature of 30°C (86°F), with not more than three current-carrying conductors in a raceway. Data is sourced from the National Electrical Code and the Copper Development Association.
Quick-jump bookmarks for common residential sizes: 14 AWG | 12 AWG | 10 AWG | 8 AWG | 6 AWG | 4 AWG | 2 AWG
| AWG / kcmil | Copper 60°C | Copper 75°C | Copper 90°C | Aluminum 75°C | Aluminum 90°C |
|---|---|---|---|---|---|
| 14 AWG | 15A | 20A | 25A | — | — |
| 12 AWG | 20A | 25A | 30A | — | — |
| 10 AWG | 30A | 35A | 40A | 30A | 35A |
| 8 AWG | 40A | 50A | 55A | 40A | 45A |
| 6 AWG | 55A | 65A | 75A | 50A | 60A |
| 4 AWG | 70A | 85A | 95A | 65A | 75A |
| 3 AWG | 85A | 100A | 115A | 75A | 85A |
| 2 AWG | 95A | 115A | 130A | 90A | 100A |
| 1 AWG | 110A | 130A | 145A | 100A | 115A |
| 1/0 AWG | 125A | 150A | 170A | 120A | 135A |
| 2/0 AWG | 145A | 175A | 195A | 135A | 150A |
| 3/0 AWG | 165A | 200A | 225A | 155A | 170A |
| 4/0 AWG | 195A | 230A | 260A | 180A | 205A |
What This Table Cannot Tell You (Derating & Limits)
The AWG wire amperage table assumes ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors bundled together. Real-world installations rarely meet both criteria. Here is how derating rows and external factors modify the base values:
1. Conduit Fill Derating
When you pull more than three current-carrying conductors through a single conduit, the wires heat each other up. You must apply a correction factor from NEC Table 310.15(C)(1). For example, if you have 4 to 6 current-carrying conductors in a pipe, you must multiply the base ampacity by 80%.
Example: You have five 12 AWG THHN wires in a conduit. The 90°C column lists 12 AWG THHN at 30A. Applying the 80% derating factor (30A x 0.80) yields a derated ampacity of 24A. However, because your breaker terminals are likely rated for 60°C/75°C, NEC 110.14(C) forces you to cap the final allowable ampacity at the 60°C column limit for 12 AWG, which is 20A. The derating calculation proves the wire won't melt in the conduit, but the terminal limit dictates your breaker size.
2. Ambient Temperature Corrections
If your conduit runs through an attic in a hot climate where temperatures routinely exceed 86°F (30°C), the wire's ability to shed heat drops. You must multiply the 90°C column value by the temperature correction factor. If the derated value falls below your breaker size, you must upsize the wire.
3. Voltage Drop
The most dangerous blind spot of the AWG wire amperage table is that it does not account for voltage drop. Ampacity only tells you the current required to overheat and melt the wire's insulation. It tells you nothing about whether the voltage at the end of a 150-foot run will be sufficient to start a compressor motor. For long runs, you must calculate voltage drop (aiming for <3% on branch circuits) and often upsize the wire by one or two AWG sizes beyond what the ampacity table demands.
AWG Wire Amperage Table FAQs
What size wire do I need for a 50 amp breaker?
For a 50-amp breaker, you need 6 AWG copper wire if your terminals are rated for 75°C (yielding 65A). If you are using NM-B (Romex) cable or your equipment terminals are only rated for 60°C, you must look at the 60°C column, which limits 6 AWG copper to 55A. While 55A technically covers a 50A breaker, many inspectors and engineers prefer 4 AWG copper (70A at 60°C) for NM-B 50A circuits to provide a thermal buffer. If using aluminum wire (like XHHW-2 for a subpanel feeder), you must use 4 AWG aluminum (65A at 75°C).
Can I use the 90°C column to size my breaker?
No. The 90°C column is almost exclusively used as a mathematical starting point for derating calculations (adjusting for ambient heat or conduit fill). Under NEC 110.14(C), the final ampacity of the circuit cannot exceed the temperature rating of the termination points. Since nearly all residential and commercial breakers, lugs, and receptacles are rated for a maximum of 75°C (and many smaller devices are limited to 60°C), your final wire size must be validated against the 60°C or 75°C columns.
Why is my 10 AWG wire limited to 30 amps when the 90°C column says 40 amps?
This is a direct result of terminal temperature limitations. While 10 AWG THHN wire has insulation that can physically withstand 40 amps at 90°C without melting, the brass or copper lugs inside your breaker and receptacles are not designed to dissipate that much heat. If you push 40 amps through a 10 AWG wire into a 60°C-rated terminal, the terminal will overheat, oxidize, and potentially cause a fire long before the wire's insulation fails. Therefore, the code limits 10 AWG to 30 amps (the 60°C column value).
Does the equipment grounding wire count for conduit derating?
No. When calculating conduit fill derating (the percentage reductions applied when bundling wires), you only count current-carrying conductors. Under NEC 310.15(C)(1), equipment grounding conductors (the bare copper or green wire) and equipment bonding jumpers are not counted. However, if you are running a neutral wire that carries significant unbalanced current or harmonic currents from non-linear loads (like LED drivers or computers), that neutral must be counted as a current-carrying conductor.
