Wire AWG Current Capacity Chart: NEC Ampacity Reference Guide

For standard residential copper wire, the maximum wire AWG current limits are: 14 AWG = 15A, 12 AWG = 20A, 10 AWG = 30A, 8 AWG = 40A, and 6 AWG = 55A. These baseline numbers come directly from the National Electrical Code (NEC) and dictate the maximum continuous load a conductor can safely carry without melting its insulation. However, simply memorizing these five numbers will eventually lead to a failed inspection or a melted terminal lug. The actual allowable ampacity shifts based on insulation temperature ratings, ambient heat, and how many wires are bundled in your conduit.

Safety Warning: Any work involving mains voltage (>50V AC) requires de-energizing the circuit, locking out the breaker, and verifying the wires are dead with a tested multimeter. NEC-style guidance provided here is for educational planning; your local Authority Having Jurisdiction (AHJ) has final authority on all installations.

The Master Wire AWG Current Chart (NEC Table 310.16)

The table below is adapted directly from NEC Table 310.16 (formerly 310.15(B)(16)), the definitive standard for conductor ampacities in the NFPA 70 National Electrical Code. It assumes an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors in a raceway or cable.

Note: Aluminum conductors smaller than 8 AWG are generally not permitted for branch circuit wiring in modern NEC editions and are excluded from this table to prevent unsafe substitutions.

Which Temperature Column Applies to Your Installation

The most common mistake DIYers make is looking at a spool of 90°C THHN wire, checking the 90°C column, and assuming they can push that higher current through the circuit. You cannot. The U.S. Department of Energy and NEC Article 110.14(C) dictate that your wire AWG current limit is bottlenecked by the lowest temperature rating of any connected component.

• The 60°C Column (Small Wires): Per NEC 110.14(C)(1)(a), circuits rated 100 amps or less, or using 14 through 1 AWG wire, must use the 60°C column for sizing. This applies even if you use 90°C THHN wire, because standard residential receptacles and small breakers are only tested and rated for 60°C terminations.
• The 75°C Column (Larger Wires & Modern Panels): For circuits over 100 amps, or wire sizes 1/0 AWG and larger, you may use the 75°C column, provided the breakers and lugs are explicitly marked with a 75°C rating (which almost all modern load centers and main lugs are).
• The 90°C Column (Derating Only): You almost never use the 90°C column for final breaker sizing. The 90°C rating (common on THHN and XHHW-2 wire) is used as your starting point to calculate derating adjustments for heat and bundling. Once derated, the final ampacity must still not exceed the 60°C or 75°C termination limits.

Derating and the Limits of This Chart

The table above assumes perfect conditions: 86°F (30°C) ambient air and a maximum of three current-carrying conductors in a single conduit. Real jobsites rarely match this. Here is how derating modifies the base value, and what the table completely fails to tell you.

How Bundling Derating Modifies Base Values

When you pull more than three current-carrying conductors through a single conduit, the wires heat each other up. NEC Table 310.15(C)(1) requires you to multiply the base ampacity by a derating factor. If you have 4 to 6 conductors, you multiply by 80%. If you have 7 to 9 conductors, you multiply by 70%. For example, if you pull four 10 AWG THHN (90°C) wires in a conduit for a multi-wire branch circuit, you start with the 90°C base of 40A. Multiply 40A by 0.80, and your new wire AWG current limit drops to 32A. Since 32A is still above the 75°C termination limit of 35A, you are safe to protect it with a 30A breaker.

What the Table Cannot Tell You: Voltage Drop

NEC Table 310.16 only protects against thermal failure (the insulation melting). It does not protect against voltage drop. A 12 AWG copper wire is rated for 20A, but if you run it 150 feet to a shed to power a table saw, the resistance of that thin wire will cause a massive voltage drop. Your saw might only see 105V, causing the motor to overheat and burn out. For runs over 50 feet, always calculate voltage drop. The general rule of thumb is to keep voltage drop under 3% for branch circuits and 5% for the total feeder-plus-branch run. If your run is long, you must upsize the wire AWG regardless of the ampacity chart.

Wire AWG Current FAQ

What size wire do I need for a 50 amp circuit?

For a standard 50-amp circuit (like an EV charger or a welder outlet), you need 6 AWG copper wire if you are using the 75°C column (which yields 65A, safely covering the 50A load). However, if the run is longer than 50 feet, you should upsize to 4 AWG copper to mitigate voltage drop. If you are using aluminum wire for a 50-amp feeder, you must use 4 AWG aluminum (rated 65A at 75°C).

Can I use the 90°C THHN wire ampacity for my breaker sizing?

No. While almost all modern wire in the US (THHN/THWN-2) is rated for 90°C, NEC 110.14(C) strictly limits the termination ampacity to the rating of the breaker or lug, which is typically 75°C or 60°C. You use the 90°C column only to apply derating factors for bundling or high ambient temperatures. Once derated, the final allowable ampacity cannot exceed the 75°C or 60°C column values for breaker sizing.

How does wire AWG current change for aluminum vs copper?

Aluminum has higher electrical resistance than copper, meaning it generates more heat at the same current. Consequently, aluminum wire has a lower ampacity rating. As a practical rule of thumb, you must go up two AWG sizes in aluminum to match the current capacity of copper. For example, to replace a 6 AWG copper feeder (65A at 75°C), you would need to use 4 AWG aluminum (also 65A at 75°C). Always use anti-oxidant paste (like Noalox) and torque aluminum lugs to exact manufacturer specifications to prevent creeping and arcing.

Does the ground wire count towards wire AWG current derating?

No. When calculating bundling derating factors under NEC 310.15(C)(1), you only count current-carrying conductors. Equipment grounding conductors (the bare copper or green wire) do not carry current under normal operation and are explicitly excluded from the count. However, if you are pulling a neutral wire for a 240V-only circuit (like a baseboard heater), the neutral does not count either. But if it is a 120/240V circuit (like a dryer), the neutral is a current-carrying conductor and must be counted for derating.