For standard residential copper wiring in a 30°C (86°F) ambient environment, use the 60°C column for 14, 12, and 10 AWG wire, and the 75°C column for 8 AWG and larger, per NEC Table 310.16 and 110.14(C). However, pulling wire through a hot attic or bundling multiple circuits in one conduit changes those numbers entirely. This guide provides the exact baseline data and the derating math you need to keep your installation safe and code-compliant.
The Master Electrical Cable Amp Chart (NEC Table 310.16)
This table is sourced directly from NFPA 70 (National Electrical Code) Table 310.16. It defines the allowable ampacities of insulated conductors rated up to 2000 volts in an ambient temperature of 30°C (86°F), with no more than three current-carrying conductors in a raceway.
The most queried sizes for residential branch circuits and feeders are 14 AWG (15A lighting), 12 AWG (20A receptacles), 10 AWG (30A dryers/RV), 6 AWG (50A ranges/EV), and 2 AWG (100A subpanels). Scroll down to find their exact limits across all temperature ratings.
| AWG / kcmil | Copper 60°C | Copper 75°C | Copper 90°C | Aluminum 60°C | Aluminum 75°C | Aluminum 90°C |
|---|---|---|---|---|---|---|
| 14 | 15 | 20 | 25 | - | - | - |
| 12 | 20 | 25 | 30 | 15 | 20 | 25 |
| 10 | 30 | 35 | 40 | 25 | 30 | 40 |
| 8 | 40 | 50 | 55 | 30 | 40 | 45 |
| 6 | 55 | 65 | 75 | 40 | 50 | 60 |
| 4 | 70 | 85 | 95 | 55 | 65 | 75 |
| 3 | 85 | 100 | 115 | 65 | 75 | 85 |
| 2 | 95 | 115 | 130 | 75 | 90 | 100 |
| 1 | 110 | 130 | 145 | 85 | 100 | 115 |
| 1/0 | 125 | 150 | 170 | 100 | 120 | 135 |
| 2/0 | 145 | 175 | 195 | 115 | 135 | 150 |
| 3/0 | 165 | 200 | 225 | 130 | 155 | 175 |
| 4/0 | 195 | 230 | 260 | 150 | 180 | 205 |
Decoding the Columns: 60°C vs. 75°C vs. 90°C
The most common mistake DIYers and junior electricians make is looking at a spool of 90°C-rated THHN wire, checking the 90°C column, and sizing the breaker accordingly. This is a fire hazard and a direct violation of NEC 110.14(C).
You must size your overcurrent protection (breaker) based on the lowest temperature rating of any component in the circuit. Most standard residential breakers and receptacles are rated for 75°C. Furthermore, NEC 110.14(C)(1)(a) mandates that for circuits 100 amps or less, or using 14 through 1 AWG wire, you must use the 60°C column for ampacity, regardless of the wire's insulation rating.
When to use the 60°C column: Sizing breakers for 14, 12, 10, 8, 6, 4, and 2 AWG circuits in standard residential panels (NM-B Romex is inherently limited to the 60°C column anyway).
When to use the 75°C column: Sizing feeders and branch circuits over 100A, or using wire sizes 1/0 AWG and larger, provided the breaker lugs are explicitly marked 75°C (most modern Square D QO and Eaton BR breakers are).
When to use the 90°C column: Never for final breaker sizing. The 90°C column is exclusively used as your starting baseline for calculating derating factors before applying the final 60°C/75°C limit.
Derating Factors: When the Base Chart Lies to You
The electrical cable amp chart above assumes two perfect conditions: an ambient air temperature of 30°C (86°F) and no more than three current-carrying conductors bundled together. In the real world, attics get hot and conduits get crowded. When these conditions change, the wire's ability to shed heat drops, and you must "derate" (reduce) the allowable ampacity.
1. Ambient Temperature Correction
If you run THHN through an attic that reaches 130°F (54°C) in the summer, you must consult NEC Table 310.15(B)(1). For 90°C wire at 51-55°C ambient, the correction factor is 0.76.
Example: 10 AWG THHN (90°C column = 40A). 40A × 0.76 = 30.4A. You can still use a 30A breaker, but if the attic hits 60°C (factor 0.63), the wire drops to 25.2A, forcing you to upsize to 8 AWG.
2. Bundling (More Than 3 Current-Carrying Conductors)
If you pull multiple circuits through a single EMT conduit, the wires heat each other up. Per NEC Table 310.15(C)(1):
- 4 to 6 conductors: Multiply base ampacity by 80%
- 7 to 9 conductors: Multiply base ampacity by 70%
- 10 to 20 conductors: Multiply base ampacity by 50%
Worked Example: You are pulling four 12 AWG THHN wires (two hots, one neutral, one ground) through a conduit. Only the hots and neutral are "current-carrying" (3 total). No bundling derating applies. But if you pull two separate 120V circuits (4 current-carrying conductors), you must derate. 12 AWG THHN at 90°C is 30A. 30A × 0.80 = 24A. Because 24A is still greater than the 20A breaker limit (and the 20A 60°C column limit), 12 AWG is legally compliant.
Table 310.16 only prevents the wire insulation from melting; it does not guarantee your appliances will get enough voltage. The NEC recommends a maximum 3% voltage drop for branch circuits and 5% total for feeders. If you run 2 AWG copper (rated 115A at 75°C) to a 100A subpanel 150 feet away, the wire won't overheat, but your voltage will drop below 114V under load, potentially damaging compressors and electronics. For long runs, always calculate voltage drop and upsize the wire accordingly.
Electrical Cable Amp Chart FAQ
Can I use the 90°C column to size my breaker for THHN wire?
No. While THHN and XHHW-2 wire insulation is rated for 90°C, the circuit breakers, lugs, and receptacles you connect them to are almost universally rated for 75°C or 60°C. Per the NEC "weakest link" rule (110.14(C)), your final breaker size cannot exceed the ampacity listed in the 60°C or 75°C column, depending on the wire size and equipment ratings. The 90°C column is only used as the mathematical starting point before applying ambient temperature and bundling derating factors.
Does the neutral wire count for bundling derating?
It depends on the circuit type. In a standard 120/240V single-phase residential feeder or multi-wire branch circuit (MWBC), the neutral only carries the unbalanced load between the two hot legs. Under NEC 310.15(C)(1), this neutral is not considered a current-carrying conductor for derating purposes. However, if you are wiring a 120V circuit where the neutral carries the exact same current as the hot wire, or a 3-phase circuit with significant harmonic loads (like LED drivers or IT equipment), the neutral does count and must be included in your bundling math.
How does the electrical cable amp chart change for aluminum wire?
Aluminum has higher electrical resistance than copper, meaning it generates more heat at the same current. Consequently, you must use a larger gauge of aluminum to achieve the same ampacity. For example, to supply a 200-amp residential service, you can use 2/0 AWG copper (175A at 75°C, permitted to round up to 200A per NEC 240.4(B) for residential services), but if using aluminum SER cable, you must step up to 4/0 AWG (180A at 75°C, also permitted to round up to 200A). Always ensure your breaker lugs are rated for aluminum and apply an antioxidant compound like Noalox to prevent galvanic corrosion.
What size wire do I need for a 60 amp EV charger?
For a continuous 60A load (like a hardwired Level 2 EV charger), the NEC requires the circuit to be rated at 125% of the continuous load, meaning you need wire and a breaker capable of handling 75 amps. If you are pulling individual THHN wires in a conduit, 4 AWG copper (85A at 75°C) is the correct choice. If you are running NM-B (Romex) cable through wall cavities, you are forced into the 60°C column; 4 AWG NM-B is rated for 70A, which is insufficient for a 75A requirement, forcing you to upsize to 3 AWG or 2 AWG NM-B, or switch to THHN in conduit. Always verify the specific terminal temperature ratings on your EVSE manufacturer's installation sheet.
