For standard residential and commercial copper wiring, the definitive wire amps table is NEC Table 310.16. If you need an immediate answer for standard branch circuits using copper wire at standard ambient temperatures: 14 AWG is 15A, 12 AWG is 20A, 10 AWG is 30A, and 6 AWG is 55A (based on the 60°C termination column).

However, pulling a single number from a chart without understanding the temperature columns and derating factors is how breakers trip and insulation melts. This guide provides the complete data table, explains exactly which column applies to your installation, and gives you a concrete decision path to size your wire correctly the first time.

Bookmark Quick-Jump: The 4 Most Queried Wire Sizes

Before diving into the full chart, here are the baseline ampacities for the most common residential branch circuit wires (Copper, 60°C column, not more than 3 current-carrying conductors in a raceway, 86°F/30°C ambient):

  • 14 AWG: 15 Amps (Strictly limited by NEC 240.4(D))
  • 12 AWG: 20 Amps (Strictly limited by NEC 240.4(D))
  • 10 AWG: 30 Amps (Strictly limited by NEC 240.4(D))
  • 6 AWG: 55 Amps (Common for 50A ranges/dryers using 75°C column adjustments)

The Master Wire Amps Table (NEC 310.16)

The following table is sourced directly from NFPA 70 (National Electrical Code) Table 310.16. It applies to copper conductors with insulation types THHN, THWN, XHHW, and similar, rated up to 90°C, in an ambient temperature of 30°C (86°F).

AWG / kcmil 60°C (140°F) Column 75°C (167°F) Column 90°C (194°F) Column
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
* The Small Conductor Rule (NEC 240.4(D)): Even though the 75°C and 90°C columns show higher numbers for 14, 12, and 10 AWG, NEC 240.4(D) strictly limits the overcurrent protection (breaker size) for these small conductors to 15A, 20A, and 30A respectively. You can only use the higher columns for these sizes when calculating derating adjustments, never for final breaker sizing.

How to Read the Table and Pick Your Column

The most common mistake DIYers and junior electricians make is defaulting to the 90°C column because it yields the highest ampacity, allowing them to use thinner, cheaper wire. This is a code violation and a fire hazard. Here is how to select the correct column based on Electrical Contractor Magazine and NEC 110.14(C) guidelines:

  • The 60°C Column: Use this for circuits rated 100 Amps or less, or for wire sizes 14 AWG through 1 AWG. Most standard residential receptacles, lighting circuits, and small appliance branches terminate on devices (receptacles, switches, breakers) rated for 60°C or are unmarked, which defaults to 60°C.
  • The 75°C Column: Use this for circuits rated over 100 Amps, or for wire sizes 1/0 AWG and larger. Most modern main breaker panels, subpanel lugs, and heavy-duty disconnects are explicitly marked 75°C.
  • The 90°C Column: Never use this column for final breaker sizing. The 90°C column is used exclusively as your starting baseline for derating calculations (adjusting for heat and bundling). Once you apply the derating math, you must compare the result back to the 60°C or 75°C column to select your final breaker.

Derating: When the Base Table Lies

The wire amps table above assumes two perfect conditions: an ambient air temperature of 86°F (30°C) and no more than three current-carrying conductors (CCCs) bundled together in a single conduit. When you violate either condition, the wire cannot dissipate heat as effectively, and you must reduce (derate) its ampacity.

1. Ambient Temperature Derating

If your conduit runs through a hot attic in the summer, the ambient temperature might be 110°F (43°C). According to NEC Table 310.15(B)(1), the correction factor for 90°C THHN wire at 110°F is 0.87.
Example: 8 AWG THHN has a 90°C baseline of 55A. 55A × 0.87 = 47.8A. You must now treat that 8 AWG wire as if it only has an ampacity of 47.8A.

2. Bundling (More than 3 CCCs)

If you pull two separate 120V circuits (2 hots, 2 neutrals = 4 CCCs) through the same piece of EMT conduit, you must apply a bundling derating factor. For 4 to 6 CCCs, NEC Table 310.15(C)(1) mandates an 80% multiplier.
Example: 12 AWG THHN (90°C baseline = 30A). 30A × 0.80 = 24A. Because 24A is still higher than the 20A limit in the 60°C column, you can still protect this wire with a standard 20A breaker. But if you bundled 10 CCCs together (50% multiplier), 30A × 0.50 = 15A. You would be forced to upsize to 10 AWG wire to maintain a 20A circuit.

For long runs, you must also calculate voltage drop. While the NEC doesn't strictly mandate a specific drop percentage for branch circuits in all cases, Southwire's voltage drop guidelines and general engineering practice dictate keeping it under 3% for branch circuits and 5% total from service to appliance.

Decision Path: Sizing Your Wire in 4 Steps

Stop guessing. Follow this exact sequence to terminate your wire sizing debate and pick a concrete part.

  1. Identify the Continuous Load: What is the maximum amperage? If the load will run for 3 hours or more (like a heater or EV charger), multiply the load by 1.25. (e.g., A 32A continuous EV charger requires 32 × 1.25 = 40A minimum wire ampacity).
  2. Establish the Base Wire (Using 75°C or 60°C): Look at the table. For a 40A requirement, 8 AWG (50A at 75°C) is your baseline. Concrete Pick so far: 8 AWG.
  3. Apply Derating (Using 90°C): Count your CCCs and check your ambient temp. Let's say you have 4 CCCs in a standard 86°F garage. Derating is 80%. Take the 90°C column for 8 AWG (55A) and multiply by 0.80 = 44A.
  4. Final Verification: Is your derated 90°C value (44A) greater than or equal to your required load (40A)? Yes. Is it protected by a breaker that doesn't exceed the 75°C column limit (50A)? Yes.
    FINAL CONCRETE PICK: Buy 8 AWG THHN Copper and protect it with a 40A or 50A breaker.

What This Wire Amps Table Cannot Tell You

While NEC 310.16 is the bible for thermal limits, it is not a complete installation manual. The table is blind to three critical real-world factors:

  • Physical Lug Sizing: You might calculate that 3 AWG wire is perfect for a 100A subpanel feeder based on the 75°C column (100A). However, if the 100A breaker lug is physically too small to accept 3 AWG, or if the manufacturer's instructions explicitly require 1/0 AWG for mechanical strength, the manufacturer's instructions override the table (NEC 110.3(B)).
  • Short Circuit Fault Current: The table tells you what the wire can handle continuously without melting. It does not tell you if the wire will withstand the explosive magnetic and thermal forces of a 10,000A short circuit before the breaker trips. That requires checking the breaker's let-through current and the wire's withstand rating.
  • Aluminum vs. Copper: The table above is strictly for Copper. If you are using Aluminum or Copper-Clad Aluminum (common for large service entrance feeders like 2/0 or 4/0 to save money), you must use the aluminum columns in 310.16, which yield significantly lower ampacities for the same physical wire size.