How this calculator works
AWG diameters form a geometric progression, with 36 AWG equal to 0.005 inch and 4/0 equal to 0.46 inch. British SWG uses a separate tabulated progression. Area follows from circular diameter and resistance per length follows from bulk resistivity divided by area. Reverse matching uses the nearest logarithmic diameter in the supported table, clamped to its end sizes; it is not a recommendation to round down a required conductor. Material values are representative at 20 C.
Formula
dAWG = 0.000127 × 92^((36-gauge)/39) m, with 4/0 represented by -3; A = pi d²/4; R/length = rho/A. SWG uses a lookup table.
Worked example
AWG 36 has diameter 0.127 mm and area about 0.0126677 mm². SWG 20 has diameter 0.9144 mm, which is a different size from AWG 20.
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Frequently asked questions
Does insulation count in wire diameter?
No. Gauge tables refer to the bare conductor; overall insulated cable diameter is larger.
Does a gauge determine current capacity?
No. Ampacity depends on material, insulation, temperature, installation and applicable electrical rules.
How are 0, 00 and 0000 represented?
The selector labels them 0, 2/0, 3/0 and 4/0. Their internal AWG indices are 0, -1, -2 and -3.