The American Wire Gauge (AWG) table is the definitive reference for determining the maximum current a conductor can safely carry without overheating. For standard residential branch circuits using copper wire, the baseline rules are straightforward: 14 AWG is rated for 15 amps, 12 AWG for 20 amps, and 10 AWG for 30 amps. These values are derived from the 60°C column of NEC Table 310.16, which governs most standard home terminations.

However, picking the right wire goes beyond memorizing three numbers. The full AWG table contains multiple temperature columns, derating factors, and material variables that dictate whether your installation will pass inspection or become a fire hazard. Below is the complete reference chart, followed by the practical jobsite rules for applying it.

The Complete NEC AWG Table (Copper, 60°C/75°C/90°C)

How to read this table: This data is sourced directly from NFPA 70 (NEC) Table 310.16 for copper conductors in a standard 30°C (86°F) ambient environment. The table is divided into three temperature columns based on the insulation type of your wire. 60°C applies to older wiring and standard NM-B (Romex) terminations. 75°C applies to most modern THHN wires in conduit and standard breaker lugs. 90°C applies to high-heat insulation (like THHN/THWN-2) but is primarily used as a starting point for derating, not for final ampacity.

Quick-Jump Reference: Bookmark this page for the most queried residential sizes:
NEC Table 310.16 - Copper Conductors (Ampacity at 30°C Ambient)
AWG Size 60°C Column (NM-B / TW) 75°C Column (THW / RHW) 90°C Column (THHN / THWN-2)
14 AWG15A*20A*25A*
12 AWG20A*25A*30A*
10 AWG30A*35A*40A*
8 AWG40A50A55A
6 AWG55A65A75A
4 AWG70A85A95A
3 AWG85A100A110A
2 AWG95A115A130A
1 AWG110A130A145A
1/0 AWG125A150A170A
2/0 AWG145A175A195A
3/0 AWG165A200A225A
4/0 AWG195A230A260A

*Note: Per NEC 240.4(D), the overcurrent protection for 14, 12, and 10 AWG copper is strictly limited to 15A, 20A, and 30A respectively, regardless of the higher values shown in the 75°C or 90°C columns.

Which Column Applies to Your Installation?

The most common mistake DIYers and junior apprentices make is looking at the 90°C column for THHN wire and assuming a 12 AWG wire can handle 30 amps. In electrical wiring, the weakest link rule dictates your final ampacity. You must use the lowest temperature rating of any component in the circuit.

The Termination Limit: Standard residential breakers and receptacles rated 100A or less are generally tested and listed for 60°C or 75°C terminations. Even if you pull 90°C THHN wire through your conduit, when that wire lands on a standard 20A receptacle, you must use the 60°C or 75°C column to determine the wire's allowable ampacity.

How Derating Rows Modify the Base Value

While you cannot use the 90°C column for final termination ampacity, you do use it as the starting point for ampacity derating. When you bundle multiple current-carrying conductors in a single conduit, they trap heat. NEC Table 310.15(C)(1) requires you to reduce the wire's capacity.

Worked Example: You are running a 240V circuit through a conduit with 4 current-carrying conductors (two hots, two neutrals for a multi-wire branch circuit). The NEC requires an 80% derating factor for 4-6 conductors.

  • Step 1: Start with the 90°C column for 12 AWG THHN (30A).
  • Step 2: Apply the derating factor: 30A × 0.80 = 24A.
  • Step 3: Compare to the overcurrent device. Your derated ampacity (24A) is greater than your 20A breaker. The wire is protected.
  • Step 4: Check termination limits. 12 AWG at 60°C is 20A. It matches the breaker perfectly. The installation is code-compliant.

What the AWG Table Cannot Tell You

The AWG table assumes ideal conditions: a short wire run, a 30°C ambient temperature, and isolated conductors. It does not account for real-world physics that can ruin a circuit. Refer to Southwire's technical engineering guides for deeper calculations on the following limitations:

  • Voltage Drop: The table assumes the wire can carry the current safely, but it doesn't guarantee the voltage will arrive at the load. For runs exceeding 100 feet, a 10 AWG wire carrying 25 amps will experience significant voltage drop. You must upsize the wire (e.g., to 8 AWG) to maintain a maximum 3% voltage drop on branch circuits, even if 10 AWG is thermally rated for the load.
  • Conduit Fill Limits: Just because a wire fits in the table doesn't mean it fits in the pipe. NEC Chapter 9, Table 1 limits conduit fill to 40% for three or more wires. You cannot physically jam six 6 AWG wires into a 1/2-inch EMT conduit, regardless of what the ampacity table says.
  • Lug Physical Sizing: Standard 100A main breaker lugs in residential load centers are typically rated to accept a maximum of 4 AWG or 2 AWG copper. If your voltage drop calculation demands 1/0 AWG wire, you will need to use a polaris connector or a larger lug kit to step down to a smaller wire for the final termination.

AWG Table FAQ: Long-Tail Questions Answered

What size wire do I need for a 50-amp hot tub or EV charger?

For a 50-amp circuit, you need wire rated for at least 50 amps. If you are using NM-B (Romex) cable indoors, you must use 6 AWG copper, which is rated for 55A in the 60°C column. If you are pulling individual THHN conductors in conduit, 8 AWG copper is technically rated for 50A in the 75°C column, but most inspectors and EV charger manufacturers explicitly require 6 AWG THHN to account for continuous load rules (125% multiplier) and voltage drop over distance. Always check the manufacturer's installation manual, as it overrides general table assumptions.

Can I use the 90°C column to size my residential breakers?

No. NEC 110.14(C) strictly limits termination temperatures. For circuits rated 100A or less, or for conductors sized 14 AWG through 1 AWG, you must use the 60°C column unless the equipment is explicitly marked and listed for 75°C. Almost no standard residential receptacles or breakers are listed for 90°C terminations. The 90°C column is exclusively a mathematical tool for calculating derating adjustments before you verify the final size against the 60°C/75°C termination limits.

How does aluminum wire change the AWG table values?

Aluminum is less conductive than copper, meaning you must use a physically larger wire to carry the same current. As a general jobsite rule of thumb, aluminum wire requires two AWG sizes larger than copper for the same ampacity. For example, if a copper feeder requires 4 AWG (85A at 75°C), the equivalent aluminum feeder must be 2 AWG (90A at 75°C). Furthermore, aluminum requires special anti-oxidant paste (like Noalox) and specific torque settings to prevent thermal expansion issues at the lugs.

Does the ground wire count towards AWG derating?

No. When calculating conduit fill derating under NEC 310.15(C)(1), you only count current-carrying conductors. Equipment grounding conductors (bare copper or green THHN) do not carry current under normal operating conditions and are therefore excluded from the derating count. However, the ground wire does count toward the physical conduit fill percentage limits outlined in NEC Chapter 9.