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Wire Size Calculator & Chart

Quick AWG reference for diameter and ampacity checks before you verify the final conductor size against the actual circuit conditions.

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Quick Wire Size Lookup

Wire Diameter by AWG (Larger number = smaller wire) 14 14 AWG 12 12 AWG 10 10 AWG 8 8 AWG 4/0 4/0 AWG Common Residential Circuits: 15A branch: 14 AWG | 20A branch: 12 AWG | 30A circuit: 10 AWG | 50A circuit: 6 AWG | 200A service: 2/0 or larger Use conductor, temperature, termination, and small-conductor rules before finalizing a wire size

Wire diameter increases as AWG number decreases. A 4/0 conductor is several times the diameter of a 14 AWG conductor.

Using The Wire Size Chart

This page is a quick reference for conductor diameter and ampacity by size. The chart is useful when you need to compare common AWG sizes, check copper versus aluminum, or get a starting point before running the full code path.

What The Chart Assumes

The reference values are only a starting point. Final conductor size can change with termination limits, insulation type, conductor count, ambient temperature, voltage drop, equipment listing, and any local amendments that apply to the job.

Common Uses

Reading AWG Sizes

AWG numbers run backward: the smaller the number, the larger the conductor. After 1 AWG, the system moves into 1/0, 2/0, 3/0, 4/0, and then kcmil sizes for larger conductors.

Why Final Verification Still Matters

A chart alone does not decide the installation. If the run is long, bundled, exposed to heat, or connected to equipment with lower-temperature terminations, the final conductor may need to be larger than the baseline reference shown here.

Reference: Complete Wire Size Chart

AWG / kcmil Diameter (in) Copper Reference Values Aluminum Reference Values Common Use
60°C 75°C 90°C 60°C 75°C 90°C
14 0.064 20 20 25 15 15 20 Light fixtures, small loads
12 0.081 20 25 30 15 20 25 General outlets, kitchen
10 0.102 30 35 40 24 30 35 Dryers, heavy loads
8 0.128 40 50 55 35 40 45 Ranges, large circuits
6 0.162 55 65 75 40 50 55 Subpanels, feeders
4 0.204 70 85 95 55 65 75 Large feeders
2 0.258 95 115 130 75 90 100 Heavy feeders
1 0.289 110 130 150 85 100 115 Service entrance, large loads
1/0 0.325 125 150 170 100 120 135 Service entrance 100A+
2/0 0.365 145 175 195 115 135 150 Service entrance 150A+
3/0 0.410 165 200 225 130 155 175 Service entrance 175A+
4/0 0.460 195 230 260 150 180 205 Service entrance 200A
250 kcmil 0.575 215 255 290 170 205 230 Heavy feeders 250A+
300 kcmil 0.632 240 285 320 190 230 255 Service 300A+
350 kcmil 0.681 260 310 350 210 250 280 Service 350A+
400 kcmil 0.728 280 335 380 225 270 305 Service 400A+
500 kcmil 0.813 320 380 430 260 310 350 Service 500A+

Frequently Asked Questions

For a typical 30A branch circuit, 10 AWG copper is the common baseline. Long runs, higher ambient temperature, bundling, aluminum conductors, and terminal limits can all push you to a larger size.
Lower numbers = bigger wire. Every 3 steps doubles the capacity. 14 is tiny, 10 is solid, 1 is huge, then you jump to 1/0 and keep going. Just check the chart—easier than remembering.
Those are temperature ratings for the conductor insulation and the connected equipment. Many modern conductors are dual-rated, but you still size from the lowest-temperature termination in the circuit.
Allowed for service entrance and feeders. Need bigger sizes than copper, costs about the same by the foot. For branch circuits, copper every time. Large services? Sometimes aluminum makes sense economically.
2/0 copper or 4/0 aluminum is a common baseline for a 200A residential service, but service equipment, utility standards, and local requirements can vary. Always verify before ordering conductors.

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