If you need the direct answer for standard residential copper branch circuits: 14 AWG is 15 amps, 12 AWG is 20 amps, 10 AWG is 30 amps, and 8 AWG is 40 amps. However, picking the right wire gauge for a subpanel feeder, an EV charger, or a long conduit run requires more than a quick glance at a blog post. You need the actual code baseline.

The definitive wire amp size chart used by electricians and inspectors in the United States is NEC Table 310.16 (formerly 310.15(B)(16)). This table dictates the allowable ampacities for insulated conductors rated up to 2000 volts. Below is the complete reference data for the most common DIY and trade sizes, followed by the critical rules on how to actually read the columns, apply derating, and avoid the most common wire-sizing mistakes.

The Master Wire Amp Size Chart (NEC Table 310.16)

How to read this table: The table is divided by conductor material (Copper vs. Aluminum) and temperature rating (60°C, 75°C, 90°C). The temperature rating corresponds to the insulation type stamped on the wire jacket. For example, standard NM-B (Romex) is rated 60°C, while THHN/THWN-2 in conduit is rated 90°C. Aluminum 60°C is omitted here as it is virtually obsolete in modern panel terminations; modern aluminum feeders use 75°C or 90°C rated insulation (like XHHW-2).
Source: NEC Table 310.16 (2020/2023 Edition) — Allowable Ampacities for 60°C to 90°C Insulated Conductors, 3 Current-Carrying Conductors in Raceway, Ambient Temperature 30°C (86°F).
AWG / kcmil Copper 60°C (NM-B) Copper 75°C Copper 90°C (THHN) Aluminum 75°C (XHHW) Aluminum 90°C (THWN-2)
14 15A 20A 25A — —
12 20A 25A 30A — —
10 30A 35A 40A — —
8 40A 50A 55A 40A 45A
6 55A 65A 75A 50A 60A
4 70A 85A 95A 65A 75A
3 85A 100A 115A 75A 85A
2 95A 115A 130A 90A 100A
1 110A 130A 145A 100A 115A
1/0 125A 150A 170A 120A 135A

Bookmark-Friendly Quick-Jump Rows

  • 15A Circuit (Lighting/Receptacles): 14 AWG Copper (60°C column).
  • 20A Circuit (Kitchen/Bath/Garage): 12 AWG Copper (60°C column).
  • 30A Circuit (Dryer/Water Heater): 10 AWG Copper (60°C column).
  • 50A Circuit (Range/EV Charger): 6 AWG Copper or 4 AWG Aluminum (using 60°C/75°C termination limits).
  • 100A Subpanel Feeder: 3 AWG Copper or 1/0 AWG Aluminum (using 75°C termination limits).

Which Temperature Column Actually Applies to Your Panel?

The most common mistake DIYers make with a wire amp size chart is looking at the 90°C column because they bought THHN wire, and assuming they can push more current through it. You almost always cannot.

The column you must use is dictated by the weakest link in the circuit, which is usually the termination lug on the breaker or receptacle. Under NEC 110.14(C), the temperature rating of the wire must be matched to the terminal rating.

The 100-Amp Rule: For circuits rated 100 amps or less, or for wire sizes 14 AWG through 1 AWG, the NEC mandates using the 60°C column unless the equipment is specifically listed and marked for 75°C. While most modern breakers (like Square D QO or Siemens QP) are rated 75°C, standard residential receptacles and older panels often are not. Therefore, for branch circuits, the 60°C column is your legal and safe baseline.

When do you use the 75°C column? You can use the 75°C column for circuits over 100A, or for wire sizes larger than 1 AWG, provided the panel and breaker lugs are rated 75°C (which nearly all modern subpanel lugs are). This is why a 100A subpanel feeder can legally use 1/0 AWG Aluminum (rated 120A in the 75°C column), but a 50A EV charger circuit must use 6 AWG Copper (rated 55A in the 60°C column, rounded down to the 50A breaker).

When do you use the 90°C column? The 90°C column is only used as the starting point for calculating derating factors (like ambient heat or bundling). The final derated ampacity must still be equal to or greater than the breaker size, and the breaker size cannot exceed the 60°C or 75°C termination limits.

Derating Factors and What the Chart Cannot Tell You

NEC Table 310.16 assumes you are running no more than three current-carrying conductors in a raceway at an ambient temperature of 30°C (86°F). The moment you change those conditions, the chart's base values are modified.

How Derating Modifies the Base Value

If you pull four or more current-carrying conductors through a single conduit, they heat each other up. You must apply a derating multiplier from NEC Table 310.15(C)(1).

Worked Example: You are running two 120V circuits in one EMT conduit (2 hots, 2 neutrals = 4 current-carrying conductors). You want to use 12 AWG THHN wire on a 20A breaker.

  1. Base Value: 12 AWG in the 90°C column is 30A.
  2. Derating Factor: 4 conductors requires an 80% multiplier.
  3. Math: 30A × 0.80 = 24A.
  4. Result: 24A is greater than your 20A breaker, so 12 AWG THHN is perfectly legal here. The termination limit (20A at 60°C) still governs the breaker size, but the wire itself won't overheat in the conduit.

If you added a third circuit to that same conduit (6 current-carrying conductors), the derating drops to 60%. 30A × 0.60 = 18A. Because 18A is less than the 20A breaker, you would be forced to upsize your wire to 10 AWG THHN or drop to a 15A breaker. For a deeper look at bundling rules, consult the National Fire Protection Association's NEC resources.

What the Wire Amp Size Chart Cannot Tell You

Table 310.16 only tells you the thermal limit of the insulation. It completely ignores three critical real-world factors:

  1. Voltage Drop: The chart says 12 AWG copper is fine for 20A. But if you run that wire 150 feet to a shed, you will experience a voltage drop of over 5%, which can damage motors and electronics. The NEC recommends keeping voltage drop under 3% for branch circuits. For long runs, you must upsize the wire (e.g., to 10 AWG or 8 AWG) purely for voltage maintenance, even if the ampacity chart says the smaller wire is safe. Use the Southwire Voltage Drop Calculator to verify long runs.
  2. Physical Lug Capacity: The chart might tell you that 1/0 AWG Aluminum is perfect for a 125A feeder. But if your main breaker's physical lug is only rated to accept up to 2 AWG wire, you cannot terminate it. You would need to use a Polaris connector or a lug kit to step down the wire size at the termination point.
  3. Short-Circuit Withstand: Ampacity is about continuous heat. 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 let-through current of your breaker and the wire's short-circuit rating.

Always treat the wire amp size chart as your starting baseline, not your final answer. Verify your termination temperatures, calculate your conduit fill and bundling derating, and run a voltage drop check for any circuit exceeding 75 feet.