If you are sizing a standard residential 120V/240V branch circuit using NM-B (Romex) cable, the baseline AWG current chart values you need are: 14 AWG for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, and 6 AWG for 55A (routinely protected at 60A via NEC 240.4(B)). However, pulling individual THHN wires in conduit or running long feeder lines changes the math entirely.
This guide provides the complete NEC Table 310.16 ampacity data, explains exactly how to read the temperature columns, and gives you a concrete decision path to pick the right wire and breaker for your specific install.
The Complete AWG Current Chart (NEC Table 310.16)
How to read this table: This data is sourced directly from the National Fire Protection Association (NFPA 70) NEC Table 310.16. The values assume an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors in a raceway or cable. The columns are split by conductor material (Copper vs. Aluminum) and insulation temperature rating (60°C, 75°C, and 90°C).
| AWG / kcmil | Copper 60°C (140°F) | Copper 75°C (167°F) | Copper 90°C (194°F) | Aluminum 75°C (167°F) | Aluminum 90°C (194°F) |
|---|---|---|---|---|---|
| 14 AWG | 15A * | 20A * | 25A * | - | - |
| 12 AWG | 20A * | 25A * | 30A * | - | - |
| 10 AWG | 30A * | 35A * | 40A * | - | - |
| 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 | 110A | 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 |
* Note: Per NEC 240.4(D), overcurrent protection for 14, 12, and 10 AWG copper conductors is strictly capped at 15A, 20A, and 30A respectively, regardless of the higher ampacities listed in the 75°C and 90°C columns.
Which Temperature Column Applies to Your Installation?
The most common mistake DIYers make with an AWG current chart is looking at the 90°C column because they bought THHN wire, and assuming they can push 40A through 10 AWG. You cannot. Sizing relies on the weakest link rule defined in NEC 110.14(C).
When to use the 75°C column: You use the 75°C column when pulling individual THHN/THWN-2 or XHHW wires through conduit, and the termination lugs at both ends (the breaker and the subpanel or receptacle) are rated for 75°C. Most modern breakers and subpanel lugs are rated 75°C.
When to use the 90°C column: The 90°C column is almost never used for determining the final breaker size. It is used exclusively as the starting baseline for derating calculations (explained below) before you check the final ampacity against the 75°C terminal limits.
How Derating Rows Modify Your Base Ampacity
The chart above assumes a perfect environment: 86°F (30°C) ambient air and no more than three current-carrying conductors in a conduit. When real-world conditions change, you must apply derating multipliers to the 90°C column (for THHN) to find your adjusted ampacity.
1. Ambient Temperature Correction (NEC Table 310.15(B)(1)):
If you run conduit through an attic that reaches 110°F (43°C), the THHN wire loses capacity. The correction factor for 90°C wire at 41-45°C is 0.87.
Example: 8 AWG THHN (55A at 90°C) × 0.87 = 47.8A. You then compare 47.8A to the 75°C column limit (50A). The lower number (47.8A) is your new maximum ampacity.
2. Conduit Fill / Bundling (NEC Table 310.15(C)(1)):
Wires generate heat. If you pull 4 to 6 current-carrying conductors in a single conduit, you must multiply the 90°C base ampacity by 80%.
Example: You are running two 240V circuits (4 hot wires total) in one conduit using 10 AWG THHN. Base 90°C ampacity is 40A. 40A × 0.80 = 32A. Because 32A is less than the 75°C terminal limit of 35A, your adjusted ampacity is 32A. However, per NEC 240.4(D), your breaker for 10 AWG is still hard-capped at 30A.
Decision Path: Picking the Exact Wire and Breaker
Use this decision-tree-table to terminate your sizing process with a concrete part pick. Do not guess; follow the logic path for your specific installation type.
| Installation Scenario | Logic Path & Column Selection | Concrete Pick (Wire & Breaker) |
|---|---|---|
| Standard 20A Indoor Receptacle Circuit (Using NM-B cable inside walls) | NM-B cable mandates the 60°C column. Target 20A. Look at 60°C Copper column. | Wire: 12/2 NM-B (Copper) Breaker: 20A Single-Pole |
| 50A EV Charger or Range (THHN in PVC conduit, 75°C rated lugs) | Conduit + 75°C lugs = 75°C column. Target 50A. 8 AWG is 50A, but 6 AWG (65A) provides buffer for voltage drop. | Wire: 6 AWG Copper THHN (or 4 AWG Aluminum XHHW) Breaker: 50A Double-Pole |
| 100A Subpanel Feeder (SER Cable or THHN in conduit, 75°C lugs) | 75°C column. Target 100A. Copper 3 AWG is exactly 100A. Aluminum 1 AWG is 100A. | Wire: 3 AWG Copper (or 1 AWG Aluminum) Breaker: 100A Double-Pole |
| Hot Attic Run (115°F) for a 30A Dryer (THHN in conduit) | Start at 90°C column for derating. 10 AWG (40A) × 0.87 temp factor = 34.8A. Check 75°C terminal limit (35A). Passes. | Wire: 10 AWG Copper THHN (Do not use NM-B here) Breaker: 30A Double-Pole |
What This AWG Current Chart Cannot Tell You
Ampacity charts only tell you the maximum current a wire can carry before its insulation melts under specific thermal conditions. They do not account for three critical real-world factors:
- Voltage Drop: The NEC does not strictly enforce voltage drop for branch circuits (it's an informational note in 310.15(B)), but IEEE Standard 141 (The Red Book) recommends keeping it under 3% for branch circuits and 5% total from service to load. If you are running a 50A EV charger 150 feet away, 6 AWG wire will result in a 4.5% voltage drop. You must upsize to 4 AWG copper to maintain efficiency and prevent charger faults, even though 6 AWG is thermally legal.
- Physical Conduit Fill: Just because you can fit six 10 AWG wires in a 1/2-inch PVC conduit electrically (after derating) doesn't mean it's legal. NEC Chapter 9, Table 1 limits conduit fill to 40% for three or more wires to prevent jamming and physical damage during the pull.
- Short-Circuit Withstand: The chart assumes steady-state heating. Under a massive short-circuit event, the breaker must trip fast enough to prevent the wire from vaporizing. This is why you cannot put a 100A breaker on 14 AWG wire, even if you theoretically 'only plan to draw 10 amps'.
