The amperage wire chart dictates the maximum continuous current a conductor can carry safely without exceeding its insulation temperature rating. For standard residential branch circuits (15A, 20A, and 30A), you will primarily use 14 AWG, 12 AWG, and 10 AWG copper wire, respectively. However, simply matching the breaker size to the wire is only half the battle; the exact ampacity depends on the insulation type, termination temperatures, and conduit fill.

This reference guide provides the complete data from NEC Table 310.16 (the definitive amperage wire chart for North American installations), explains how to read the temperature columns, and breaks down the derating factors that modify these base values in real-world jobsite conditions.

The Master Amperage Wire Chart (NEC Table 310.16)

Before pulling wire, you must understand how to read the chart below. The National Electrical Code (NEC) categorizes ampacity by conductor material (Copper vs. Aluminum) and temperature rating (60°C, 75°C, and 90°C).

Which column applies to your installation? Modern circuit breakers and receptacles are typically rated for 75°C terminations, meaning you can use the 75°C column for sizing. However, NEC 110.14(C) requires you to use the 60°C column if the equipment is marked for 60°C, if it's an older installation, or if you are using 14, 12, or 10 AWG wire on circuits rated 100A or less (unless the equipment is explicitly listed for 75°C). Even if you pull 90°C THHN wire, your final ampacity is almost always capped by the 60°C or 75°C termination rating of the breaker or lug.
Source: NEC Table 310.16 (2023/2026 Cycle) - Allowable Ampacities of Insulated Conductors Rated Up to and Including 2000 Volts, in Ambient Temperature of 30°C (86°F).
Size (AWG/kcmil) Copper 60°C (140°F) Copper 75°C (167°F) Copper 90°C (194°F) Aluminum 75°C (167°F) Aluminum 90°C (194°F)
14 AWG *152025——
12 AWG *202530——
10 AWG *303540——
8 AWG4050554045
6 AWG5565755060
4 AWG7085956575
3 AWG851001157585
2 AWG9511513090100
1 AWG110130145100115
1/0 AWG125150170120135
2/0 AWG145175195135150
3/0 AWG165200225155170
4/0 AWG195230260180205

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

Derating Factors and the Limits of the Chart

The numbers in the amperage wire chart above assume ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a raceway. Real-world installations rarely match this baseline. You must apply derating factors from NFPA 70 (NEC) Article 310.15 to modify the base values.

How Derating Rows Modify the Base Value

When you bundle more than three current-carrying conductors in a single conduit, the trapped heat reduces the wire's ability to dissipate thermal energy. You must multiply the 90°C base ampacity by the adjustment factor in NEC Table 310.15(C)(1).

  • 4 to 6 conductors: 80% adjustment factor
  • 7 to 9 conductors: 70% adjustment factor
  • 10 to 20 conductors: 50% adjustment factor

Worked Example: You are pulling two 120V multi-wire branch circuits (4 current-carrying conductors total) through a single EMT conduit using 12 AWG THHN. The 90°C column lists 12 AWG THHN at 30A. Applying the 80% derating factor (30A × 0.80) yields an adjusted ampacity of 24A. Because 24A is still greater than the 20A termination limit, you can legally protect this circuit with a standard 20A breaker. If you had 7 conductors in that pipe (70% factor), the adjusted ampacity would drop to 21A, which still passes for a 20A breaker, but leaves almost zero margin for error.

What the Amperage Wire Chart Cannot Tell You

While NEC Table 310.16 is the law for thermal safety, it is entirely blind to two critical physical realities:

  1. Voltage Drop: The chart does not account for distance. A 100-foot run of 12 AWG copper carrying a full 20A load at 120V will experience a voltage drop of roughly 7.9V (about 6.5%). While perfectly legal under the ampacity chart, this severe drop will cause LED flicker, poor motor starting torque, and wasted energy as heat. For runs over 50 feet, you must calculate voltage drop (aiming for <3% on branch circuits) and size up the wire accordingly.
  2. Conduit Fill Capacity: Just because the ampacity math allows you to pull ten 10 AWG wires through a 1/2-inch EMT conduit doesn't mean they will physically fit. NEC Chapter 9, Table 1 limits conduit fill to 40% for three or more wires to prevent jamming and insulation damage during the pull.
Safety Caveat: Always verify local codes. Some municipalities amend the NEC to mandate voltage drop calculations as a strict requirement rather than a recommendation, and local AHJs (Authority Having Jurisdiction) always have the final say on conductor sizing.

Amperage Wire Chart FAQ

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

For a standard 50-amp circuit (like an electric range, welder, or EV charger), you need 6 AWG copper or 4 AWG aluminum. This assumes your breaker and receptacle terminations are rated for 75°C, which is standard for modern 50A equipment. If you are connecting to older equipment or specific terminal blocks explicitly marked for 60°C, you must step up to 4 AWG copper. Never use 8 AWG copper for a 50A breaker; while some specific motor circuits allow exceptions under Article 430, standard branch circuits strictly require 6 AWG.

Can I use the 90°C column for my home wiring ampacity?

Almost never for the final, legal ampacity limit. You use the 90°C column only as the starting baseline for derating calculations (as shown in the conduit fill example above). The final calculated ampacity cannot exceed the temperature rating of the weakest link in the circuit, which is almost always the breaker lug or receptacle termination (rated 60°C or 75°C). For example, even though 10 AWG THHN is rated 40A in the 90°C column, you cannot put it on a 40A breaker because the breaker terminals are likely only rated for 75°C (where 10 AWG is limited to 35A) or 60°C (limited to 30A).

Does this amperage wire chart apply to DC solar wiring?

Yes, the thermal ampacity limits in NEC Table 310.16 apply to both AC and DC conductors. However, DC systems (especially 12V, 24V, or 48V solar battery banks) are incredibly sensitive to voltage drop. A 3% voltage drop on a 120V AC circuit is 3.6V, which most appliances won't notice. A 3% drop on a 12V DC system is 0.36V, which can severely cripple the charging efficiency of an MPPT charge controller or trigger low-voltage disconnects on an inverter. For DC solar runs, it is standard practice to size the wire 2 or 3 AWG sizes larger than the ampacity chart strictly requires to keep voltage drop under 1% to 2%. For deeper DC sizing frameworks, reference resources like the Mike Holt NEC code forums which frequently cover renewable energy-specific derating scenarios.