Convert American Wire Gauge (AWG) to diameter in millimeters and inches, plus cross-sectional area.
Electrical • AWG
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American Wire Gauge (AWG) is the US standard for wire thickness, and the number runs backwards — a smaller AWG number means a thicker wire. This chart converts AWG to diameter in millimeters and inches plus cross-sectional area in mm².
Electricians, makers, and audio/automotive hobbyists use it to pick the right wire for a given current and to match US and metric specs. As a rule of thumb, every 6 AWG steps roughly halves or doubles the wire's diameter.
American Wire Gauge is a logarithmic scale that runs backwards: larger gauge numbers mean thinner wire. The system derives from manufacturing, where gauge counted how many times a wire was drawn through progressively smaller dies, so more draws meant thinner wire and a higher number. The scale is geometric, with a ratio of 92^(1/39) between consecutive gauges. Two useful consequences follow: six gauge steps roughly halve the diameter, and three gauge steps roughly halve the cross-sectional area — which is what actually determines current capacity and resistance.
Diameter (mm) = 0.127 × 92^((36 − n) ÷ 39)Area (mm²) = π × (diameter ÷ 2)²Every 6 gauges ≈ half the diameter; every 3 gauges ≈ half the areawhere:
Assumptions: AWG applies to solid round conductors. Stranded wire of the same nominal gauge has a slightly larger overall diameter and marginally less copper. Ampacity depends on insulation type, ambient temperature and bundling, so always consult the electrical code rather than the geometry alone.
Compute the dimensions of the most common household circuit wire, then test the halving rules.
Result12 AWG = 2.05 mm diameter, 3.31 mm² cross-section
In US practice 12 AWG is the standard for 20-amp circuits and 14 AWG for 15-amp. Because area halves every three gauges, substituting 14 AWG on a 20-amp circuit removes about a third of the copper — which is a fire risk, not a minor deviation.
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