If you need the direct answer for standard residential branch circuits: 14 AWG is rated for 15 amps, 12 AWG for 20 amps, 10 AWG for 30 amps, and 8 AWG for 40 amps. However, pulling a single number from a wire gauge size chart without understanding the temperature columns and termination limits is the most common cause of failed electrical inspections and overheated panels.

The chart below is based on copper conductors in standard ambient temperatures (30°C / 86°F). Before you pull wire, you must understand which column actually applies to your specific installation, how bundling wires changes the math, and what this chart completely fails to tell you about long runs.

How to Read This Wire Gauge Size Chart

The data below is sourced directly from NEC Table 310.16 (formerly 310.15(B)(16) in older code cycles), the definitive standard published by the National Fire Protection Association (NFPA). The table is divided into three temperature columns: 60°C (140°F), 75°C (167°F), and 90°C (194°F).

The Weakest Link Rule (NEC 110.14(C)): You cannot simply use the highest ampacity number on the chart. Your allowable ampacity is limited by the lowest temperature rating of any connected component. If you are using 90°C THHN wire, but your breaker terminals are only rated for 60°C (standard for most residential breakers under 100A), you must use the 60°C column to size your breaker, regardless of the wire's insulation rating.

Which column applies to your installation?

  • 60°C Column: Applies to standard non-metallic sheathed cable (NM-B / Romex), UF-B cable, and any circuit terminated on standard residential breakers or receptacles rated 100A or less.
  • 75°C Column: Applies to most feeder cables (like SER or THWN-2 in conduit) terminating in modern main panels, subpanels, and breakers rated over 100A.
  • 90°C Column: Rarely used for final breaker sizing in residential work. It is primarily used as the starting baseline for calculating ampacity derating when wires are bundled in conduit or exposed to high ambient heat.

The Master Wire Gauge Size Chart (Copper, NEC Table 310.16)

Below is the complete ampacity reference for copper conductors. Bookmark the quick-jump rows for the most common residential sizes. The 'Max Standard Breaker' column reflects standard NEC 240.4(B) next-size-up rules where applicable, but assumes standard residential termination limits.

AWG / kcmil Size 60°C (NM-B / Romex) 75°C (THWN / Feeders) 90°C (THHN / Derating Base) Max Standard Breaker
14 AWG 15A 20A 25A 15A
12 AWG 20A 25A 30A 20A
10 AWG 30A 35A 40A 30A
8 AWG 40A 50A 55A 40A (50A if 75°C term)
6 AWG 55A 65A 75A 60A
4 AWG 70A 85A 95A 80A (or 100A feeder)
3 AWG 85A 100A 110A 100A
2 AWG 95A 115A 130A 125A
1 AWG 110A 130A 145A 150A
1/0 AWG 125A 150A 170A 150A
2/0 AWG 145A 175A 195A 175A (or 200A service)
3/0 AWG 165A 200A 225A 200A
4/0 AWG 195A 230A 260A 225A (or 200A+ service)

Derating, Edge Cases, and What the Table Cannot Tell You

A wire gauge size chart based on NEC Table 310.16 only tells you the base thermal limit of a single wire in a 30°C room. It does not account for real-world installation physics.

How Derating Modifies the Base Value

When you pull multiple current-carrying conductors through a single conduit, they heat each other up. NEC 310.15(C)(1) requires you to apply an adjustment factor. This is where the 90°C column becomes vital. According to industry standard practices documented by EC&M, you calculate derating using the 90°C ampacity, then compare it to your termination limits.

Worked Example: You are pulling four current-carrying conductors (two 240V circuits) in a single EMT conduit using 12 AWG THHN.

  1. Base 90°C ampacity for 12 AWG = 30A.
  2. Four conductors require an 80% derating factor (NEC Table 310.15(C)(1)).
  3. 30A × 0.80 = 24A adjusted ampacity.
  4. However, your breaker terminals are rated 60°C (max 20A for 12 AWG).
  5. Result: The wire is thermally safe at 24A, but your breaker cannot exceed 20A due to the termination limit. You are cleared to use a 20A breaker.

What the Table Cannot Tell You

Voltage Drop: Table 310.16 only prevents the wire from catching fire; it does not guarantee your equipment will run correctly. If you run a 12 AWG wire 120 feet to a 15A receptacle, the wire won't melt, but you will experience a voltage drop of roughly 5.4V (4.5%). For sensitive electronics or motors, this causes overheating and failure. As a rule of thumb, limit voltage drop to 3% on branch circuits and 5% total from the utility transformer to the furthest outlet. Long runs require upsizing the wire gauge beyond what the ampacity chart demands.

Furthermore, this chart tells you nothing about conduit fill (NEC Chapter 9, Table 1). You might thermally derate perfectly for six 10 AWG wires in a 3/4-inch conduit, but physically, you will violate the 40% conduit fill maximum and fail the physical pull inspection.

Wire Gauge Size Chart FAQ

What wire gauge size chart applies to aluminum branch circuits?

Aluminum conducts electricity less efficiently than copper, requiring a larger physical diameter for the same ampacity. If you are using modern AA-8000 series aluminum alloy wire (as required by NEC 310.14), you must look at the aluminum columns in Table 310.16. Generally, aluminum needs to be upsized by two AWG steps compared to copper. For example, to achieve the 55A ampacity of 6 AWG copper, you must use 4 AWG aluminum. Never use legacy, uncoated aluminum wire for branch circuits due to oxidation and fire risks at terminals.

Why does my wire gauge size chart show a 90°C column I can't use for breakers?

The 90°C column exists almost entirely for derating math and high-temperature ambient environments. While your breaker lugs might only be rated for 60°C or 75°C, the wire insulation itself can safely handle 90°C. Code allows you to use the 90°C ampacity as your starting baseline when calculating adjustments for conduit bundling or hot attics, provided the final calculated ampacity does not exceed the termination temperature limit of the breaker or lug.

How do I read a wire gauge size chart for a 50-amp EV charger or hot tub?

A 50-amp circuit requires wire rated for at least 50 amps. Looking at the chart, 8 AWG copper in the 75°C column is rated exactly 50A, making it the minimum size if your EV charger hardwire terminals are rated 75°C. However, if you are using NM-B (Romex) cable, you are forced into the 60°C column, where 8 AWG is only rated 40A. Therefore, an NM-B installation for a 50A EV charger requires upsizing to 6 AWG copper (rated 55A at 60°C). Always check the manufacturer's installation manual for specific termination temperature ratings.

Does the ground wire size match the hot wire on a gauge chart?

Not necessarily. The equipment grounding conductor (EGC) is sized based on the rating of the overcurrent protective device (the breaker), not the size of the current-carrying conductors. Per NEC Table 250.122, a 15A or 20A circuit only requires a 14 AWG or 12 AWG ground, respectively. A 30A circuit requires a 10 AWG ground, and a 50A circuit requires an 8 AWG ground. If you upsized your hot wires solely to mitigate voltage drop over a long distance, you are generally not required to upsize the ground wire proportionally unless the fault current clearing time is compromised, though many inspectors prefer to see it upsized for mechanical durability in long conduit pulls.