Wire Gauge Actual Size Chart: AWG Dimensions, Ampacity & NEC Columns

The physical diameter of a wire is defined by the American Wire Gauge (AWG) standard (ASTM B258), while its safe current capacity (ampacity) is governed by NEC Table 310.16. For standard residential solid copper wire, 14 AWG has a bare diameter of 1.628 mm (0.0641") and is rated for 15A; 12 AWG is 2.053 mm (0.0808") for 20A; and 10 AWG is 2.588 mm (0.1019") for 30A. These baseline numbers dictate everything from breaker selection to conduit fill calculations.

How to Read the Wire Gauge Actual Size Chart

Before pulling wire, you need to understand how to read the intersecting physical and thermal data in a comprehensive wire gauge actual size chart. The physical dimensions (Diameter and Area) are absolute and based on the bare conductor. The ampacity columns, however, are highly conditional.

Quick-Jump Reference: Most Queried AWG Sizes

Bookmark this section for the most common residential and light-commercial wire pulls. These quick-jump rows pair the physical size with standard applications to save you a trip to the supply house.

• 12 AWG (0.0808" / 20A Max): The standard for 20A kitchen and bathroom receptacle circuits. Fits comfortably in standard single-gang boxes without excessive crowding.
• 10 AWG (0.1019" / 30A Max): Used for 30A dryers, RV outlets (NEMA 10-30 or 14-30), and heavy-duty window AC units. Requires a larger conduit bend radius than 12 AWG.
• 6 AWG (0.1620" / 55A-65A Max): The go-to size for 50A EV charger hardwires (using the 75°C column for 65A capacity, protected at 50A) and 60A subpanel feeders (derated to 55A at 60°C terminations).
• 4 AWG (0.2043" / 70A-85A Max): Standard for 100A subpanel feeders when using copper, though aluminum (2 AWG SER) is more common for this application due to cost.
• 2 AWG (0.2576" / 95A-115A Max): Frequently used for 100A to 125A service entrance conductors and heavy-duty workshop subpanels.
• 4/0 AWG (0.4600" / 195A-230A Max): The standard copper size for 200A residential service entrances. Measures just under half an inch in bare diameter, requiring 2-inch conduit minimum for standard pulls.

What This Chart Cannot Tell You (Derating & Limits)

A common mistake on the jobsite is treating the ampacity column as an absolute law. The wire gauge actual size chart provides baseline thermal limits under perfect conditions. It fails to account for three critical real-world variables.

1. Bundling Derating (NEC 310.15(C)(1))

When you pull more than three current-carrying conductors through a single raceway, they heat each other up. You must apply a derating multiplier to the 90°C column (not the final breaker column).

Example: You are pulling four 8 AWG THHN current-carrying conductors in a conduit for a multi-wire branch circuit. The 90°C ampacity for 8 AWG is 55A. For 4-6 conductors, the derating factor is 80%.
55A × 0.80 = 44A.
You must now protect this wire at the next standard breaker size down, which is 40A. If you had used the 75°C column (50A) as your baseline, your math would be wrong, and you'd fail inspection.

2. Voltage Drop Over Distance

The chart assumes the wire is infinitely short. In reality, copper has resistance (12 AWG is roughly 1.93 ohms per 1,000 feet). If you run a 12 AWG wire on a 20A circuit for 150 feet, the voltage drop is approximately 11.5V on a 120V circuit (nearly 10%). NEC 210.19(A)(Informational Note) recommends a maximum 3% drop for branch circuits. For a 150-foot run at 20A, you must upsize to 8 AWG copper to maintain voltage stability, even though 12 AWG is thermally rated for the breaker.

3. Ambient Temperature Corrections

The ampacities in the table assume an ambient temperature of 30°C (86°F). If you are routing wire through an attic in a southern climate where ambient temperatures regularly hit 50°C (122°F), you must apply a temperature correction factor from NEC Table 310.15(B)(1), which will significantly reduce the wire's safe current capacity.