For standard residential and light commercial copper branch circuits, the baseline AWG wire amps are: 14 AWG = 15A, 12 AWG = 20A, 10 AWG = 30A, 8 AWG = 40A, and 6 AWG = 55A. These values are derived from the 60°C column of NEC Table 310.16, which governs circuits rated 100 amps or less. If you are pulling individual THHN wires in conduit for a circuit over 100A, you will use the 75°C column, bumping 6 AWG to 65A and 4 AWG to 85A.
The Master AWG Wire Amps Chart (NEC Table 310.16)
How to read this table: This chart applies strictly to copper conductors with common insulation types (THHN, THWN-2, XHHW). The values assume an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors bundled in a single raceway or cable. Bookmark the quick-jump rows below for the most frequently queried residential sizes.
| AWG Size | 60°C (140°F) Branch Circuits ≤100A / NM-B |
75°C (167°F) Feeders >100A / THHN in Conduit |
90°C (194°F) Derating Calculations Only |
|---|---|---|---|
| 14 AWG | 15A | 20A | 25A |
| 12 AWG | 20A | 25A | 30A |
| 10 AWG | 30A | 35A | 40A |
| 8 AWG | 40A | 50A | 55A |
| 6 AWG | 55A | 65A | 75A |
| 4 AWG | 70A | 85A | 95A |
| 3 AWG | 85A | 100A | 110A |
| 2 AWG | 95A | 115A | 130A |
| 1 AWG | 110A | 130A | 145A |
| 1/0 AWG | 125A | 150A | 170A |
Which Temperature Column Applies to Your Installation?
The most common mistake DIYers make is sizing wire using the 90°C column because it offers the highest ampacity. Under NEC 110.14(C) termination rules, your final allowable ampacity is bottlenecked by the lowest temperature rating of any component in the circuit, including the breaker lugs, receptacles, and the wire insulation itself.
The 75°C Column: You may use this column for circuits over 100A, or for conductors 1 AWG and larger, provided the equipment terminations are explicitly marked for 75°C. This is standard for individual THHN/THWN-2 wires pulled through conduit terminating in modern commercial panels or subpanels.
The 90°C Column: This column is almost never used for final breaker sizing. It exists primarily as the starting point for derating calculations. You calculate your adjusted ampacity using the 90°C column, but the final result cannot exceed the 60°C or 75°C limits dictated by your terminations.
Derating: When Base Ampacity Drops
The base values in Table 310.16 assume ideal conditions: 30°C (86°F) ambient air and a maximum of three current-carrying conductors (CCCs) in a raceway. When conditions worsen, the wire's ability to shed heat drops, and you must derate the ampacity.
Bundling Derating (NEC Table 310.15(C)(1)):
If you pull 4 to 6 CCCs in a single conduit, you must multiply the base ampacity by 80%. For 7 to 9 CCCs, the multiplier drops to 70%.
Worked Example: You are running a 240V circuit to a hot tub using four 10 AWG THHN wires in a conduit (two hots, one neutral, one ground = 3 CCCs, but let's assume you added a second neutral for a multi-wire branch circuit, making it 4 CCCs).
1. Start at the 90°C column for 10 AWG: 40A.
2. Apply the 80% bundling factor: 40A × 0.80 = 32A.
3. Check termination limits: Your hot tub lugs are rated 75°C (35A limit for 10 AWG).
4. Result: The adjusted ampacity is 32A. Because 32A is not a standard breaker size, NEC 240.4(B) allows you to round up to the next standard size, which is 35A. However, if your terminations were only rated 60°C (30A limit), you would be forced to upsize to 8 AWG wire to maintain a 35A or 40A breaker.
Decision Tree: Picking Your Exact Wire Size
Use this decision path to terminate your sizing process with a concrete material pick. Do not guess; follow the load and installation type to your exact match.
| Installation Scenario | IF Conditions | THEN BUY (Concrete Pick) |
|---|---|---|
| Standard 15A Receptacles (Bedrooms, Living Rooms) | Load ≤ 15A, run inside finished walls, standard 60°C terminations. | 14 AWG NM-B (Romex) on a 15A breaker. |
| Kitchen/Bath/Basement 20A Receptacles | Load ≤ 20A, NEC requires 20A for small-appliance and bathroom branches. | 12 AWG NM-B on a 20A breaker. |
| 50A Range or Hot Tub (Conduit Run) | Load = 50A, individual wires in conduit, equipment lugs rated 75°C. | 6 AWG THHN Copper (65A capacity) on a 50A breaker. |
| 100A Subpanel Feeder (Conduit Run) | Load = 100A, 4 wires in conduit, 75°C lugs on main and subpanel. | 3 AWG THHN Copper OR 1 AWG XHHW Aluminum on a 100A breaker. |
| Long Run (>100 ft) 20A Receptacle | Load = 20A, but distance causes >3% voltage drop on 12 AWG. | 10 AWG NM-B on a 20A breaker (upsized strictly for voltage drop). |
What This Table Cannot Tell You
While NEC Table 310.16 is the gold standard for ampacity, it has strict boundaries. Relying on it blindly will cause failures in three specific edge cases:
- Voltage Drop: Table 310.16 only prevents the wire from melting; it does not guarantee your equipment will receive adequate voltage. For any run exceeding 100 feet, you must calculate voltage drop. A 12 AWG wire on a 20A breaker is legally safe at 150 feet, but your power tools will bog down due to a 6% voltage drop. Upsize to 10 AWG or 8 AWG for long runs.
- Aluminum Sizing: The table above is exclusively for copper. If you are using aluminum (common for feeders and service entrances due to cost), you must use the aluminum columns in Table 310.16. As a rule of thumb, aluminum requires a wire size two steps larger than copper for the same ampacity (e.g., use 2 AWG Aluminum where you would use 4 AWG Copper for an 85A load).
- Physical Lug Constraints: A 1/0 AWG wire might have the correct ampacity for a 150A breaker, but it may physically fail to fit into the lug hole of a standard residential 150A main breaker. Always check the manufacturer's datasheet for the panel's maximum lug wire size before purchasing large-gauge feeders.
When in doubt, or if your local municipality has adopted amendments to the National Electrical Code, consult your local Authority Having Jurisdiction (AHJ). The AHJ always has the final say on code compliance and inspection sign-offs.
