The direct answer for standard residential copper wire sizes is straightforward: 14 AWG is 15A, 12 AWG is 20A, 10 AWG is 30A, 8 AWG is 40A, 6 AWG is 55A, 4 AWG is 70A, and 2 AWG is 95A. However, those numbers only apply if you are using the 60°C temperature column. If you are pulling THHN in conduit and terminating on 75°C rated lugs, an 8 AWG wire is actually good for 50A, and a 6 AWG is good for 65A. To size wire legally and safely, you must use the official wire amperage table from NEC Table 310.16, selecting the correct temperature column based on your specific termination points and applying derating factors for your installation environment.
How to Read the NEC Wire Amperage Table
The National Electrical Code (NEC) Table 310.16 is the master reference for conductor ampacity in the United States. Before you pick a wire size, you need to understand how to read the columns, as picking the wrong one is the most common mistake DIYers make.
NEC Article 110.14(C) dictates the rules for temperature columns. For circuits rated 100A or less, or for wires sized 14 AWG through 1 AWG, you must use the 60°C column unless your equipment (breakers, lugs, receptacles) is explicitly marked for 75°C. For circuits over 100A or wires larger than 1 AWG, you default to the 75°C column. The 90°C column is almost never used for final ampacity; it exists primarily as a mathematical starting point for derating calculations.
The table is split into two main material sections: Copper and Aluminum. Copper is the standard for residential branch circuits and indoor feeders due to its high conductivity and physical durability. Aluminum is lighter and significantly cheaper, making it the standard for service entrance cables (like 4/0-4/0-2/0 SER) and long outdoor feeder runs, but it requires larger wire sizes to carry the same current and must be terminated with specific anti-oxidant compound and torque settings.
The Master Wire Amperage Table (NEC 310.16)
Below is the complete data table for standard residential and light commercial sizes. Source Standard: NFPA 70 (NEC) Table 310.16. Values represent the maximum allowable ampacity for up to three current-carrying conductors in a raceway at an ambient temperature of 30°C (86°F).
Bookmark-Friendly Quick-Jump: The most queried rows for residential branch circuits (15A to 50A) are bolded below.
| Size (AWG/kcmil) | Copper 60°C | Copper 75°C | Copper 90°C | Aluminum 75°C | Aluminum 90°C |
|---|---|---|---|---|---|
| 14 AWG | 15 | 20 | 25 | — | — |
| 12 AWG | 20 | 25 | 30 | — | — |
| 10 AWG | 30 | 35 | 40 | — | — |
| 8 AWG | 40 | 50 | 55 | 40 | 45 |
| 6 AWG | 55 | 65 | 75 | 50 | 60 |
| 4 AWG | 70 | 85 | 95 | 65 | 75 |
| 3 AWG | 85 | 100 | 110 | 75 | 85 |
| 2 AWG | 95 | 115 | 130 | 90 | 100 |
| 1 AWG | 110 | 130 | 145 | 100 | 115 |
| 1/0 AWG | 125 | 150 | 170 | 120 | 135 |
| 2/0 AWG | 145 | 175 | 195 | 135 | 150 |
| 3/0 AWG | 165 | 200 | 225 | 155 | 175 |
| 4/0 AWG | 195 | 230 | 260 | 180 | 205 |
| 250 kcmil | 215 | 255 | 290 | 205 | 230 |
Derating and What the Table Cannot Tell You
The wire amperage table provides the base thermal limit for a wire in a perfect scenario: an ambient temperature of 30°C (86°F) with no more than three current-carrying conductors bundled together. Real-world jobsites rarely match this baseline.
How derating rows modify the base value:
When you pull wires through a hot attic or bundle multiple circuits in a single conduit, the wires cannot dissipate heat efficiently. You must apply adjustment factors from NEC Table 310.15(C)(1). For example, if you pull 4 to 6 current-carrying conductors in one conduit, you must multiply the base ampacity by 80%. If you have 7 to 9 conductors, you multiply by 70%. Pro tip: You are legally allowed to use the 90°C column as your starting base for these derating math equations, which often allows you to keep a smaller wire size than if you started from the 75°C column.
What the table cannot tell you:
- Voltage Drop: The table only prevents the wire insulation from melting; it does not guarantee your equipment will get enough voltage. The NEC recommends a maximum 3% voltage drop on branch circuits and 5% total for feeders. A 14 AWG wire might be thermally rated for 15A, but if you run it 150 feet to a 12A space heater, the voltage drop will cause the heater to underperform and the wire to run hotter than expected.
- Physical Lug Fit: A 250 kcmil aluminum wire might have the exact right ampacity for a 200A service, but it physically will not fit into the terminal lugs of many standard 200A residential main breakers without using a mechanical lug reducer or stepping up to a panel specifically rated for larger conductors.
- Short-Circuit Withstand: The table assumes normal operating loads. It does not tell you if the wire can survive the magnetic and thermal forces of a 10,000-amp short circuit before the breaker trips. That requires checking the specific let-through current ratings of your breaker and wire pairing.
For deeper code interpretations and visual guides on conductor bundling, Mike Holt's NEC resources remain one of the most reliable supplementary references for translating codebook tables into actual jobsite practice.
Wire Amperage Table FAQ
What size wire do I need for a 50 amp breaker?
For a standard 50-amp circuit (like an EV charger or a large welder), you need 6 AWG copper wire. If you are using THHN/THWN in conduit, the 75°C column rates 6 AWG at 65A, which safely covers the 50A breaker. If you are using NM-B (Romex) inside a wall, you are forced to use the 60°C column, where 6 AWG is rated for 55A—which still legally protects a 50A load. Never use 8 AWG for a 50A breaker, as its maximum rating in the 60°C column is only 40A.
Can I use the 90°C column for my whole house wiring?
No. While modern THHN wire bought at the hardware store has insulation rated for 90°C, the breakers, receptacles, and switches you connect it to are almost universally rated for 60°C or 75°C. NEC 110.14(C) strictly requires you to use the lowest temperature rating of any connected component in the circuit. Therefore, your final ampacity is capped by the 60°C or 75°C column, regardless of the wire's 90°C capability.
How does bundling wires in a conduit change the wire amperage table values?
When you bundle more than three current-carrying conductors (hot wires and neutral, but typically not the ground wire) in a single raceway, the trapped heat reduces the wire's capacity. You must apply a derating multiplier to the 90°C column base value. For 4-6 wires, multiply the 90°C ampacity by 0.80. For 7-9 wires, multiply by 0.70. If the resulting derated number is still higher than your breaker size, the wire is safe to use.
Does the wire amperage table apply to low voltage DC systems like solar or 12V vans?
The NEC table is designed primarily for AC systems and DC systems over 50V (covered under NEC Article 690 for solar). For 12V, 24V, or 48V off-grid DC battery banks and van builds, thermal ampacity is rarely the limiting factor—voltage drop is. A 10 AWG wire can safely carry 30A thermally, but pushing 30A through 10 feet of 10 AWG wire at 12V will result in a massive voltage drop that will starve your inverter and cause low-voltage disconnects. For sub-50V DC, always size your wire using a dedicated DC voltage drop calculator targeting a maximum 1% to 2% drop, which usually results in much thicker wire than the NEC thermal table requires.
