AWG Wire Table
American Wire Gauge diameter, area, resistance and ampacity.
Overview
The AWG Wire Table is a lookup and calculator for American Wire Gauge. Enter a gauge number and read off the wire's diameter in millimetres and inches, cross-sectional area in square millimetres, resistance per kilometre and typical ampacity for chassis or transmission wiring.
It is built for electricians sizing branch circuits, hobbyists choosing battery cables and engineers translating between AWG and the metric specs that show up in international datasheets. The table covers everything from delicate 40-gauge magnet wire to chunky 0000 (4/0) service cable.
How it works
AWG is a geometric progression: each step up in gauge number reduces the diameter by a factor of 92^(1/39). Specifically the diameter in inches for gauge n is 0.005 * 92^((36 - n) / 39). The cross-sectional area scales as the diameter squared.
Resistance per length is computed from copper resistivity ρ = 1.68 * 10^-8 ohm-metres at 20 °C divided by the area. Ampacity values follow common NEC chassis and transmission-line rules of thumb, not absolute maximums — derate for bundling, insulation type and ambient temperature.
Examples
AWG 12 → 2.05 mm diameter, 3.31 mm^2 area, 5.21 Ω/km, 41 A chassis
AWG 18 → 1.02 mm diameter, 0.82 mm^2 area, 20.95 Ω/km, 16 A chassis
AWG 24 → 0.51 mm diameter, 0.205 mm^2 area, 84.2 Ω/km, 3.5 A chassis
AWG 0000 (4/0) → 11.68 mm diameter, 107 mm^2 area, 0.16 Ω/km, 380 A chassis
FAQ
Why do larger numbers mean smaller wire?
AWG was originally defined by how many times a wire was drawn through reducing dies. More draws meant a thinner wire and a larger gauge number.
Is ampacity the same as the maximum current?
No. Ampacity is a continuous-current rating under defined conditions. Short pulses tolerate more; bundled or insulated wire tolerates less.
Does the resistance figure include connectors and terminations?
No, it is the bare-copper resistance per kilometre at 20 °C. Real circuits add contact resistance at every junction.
How do AWG and metric square-millimetres relate?
Metric cable is sized by cross-sectional area in mm2. AWG 12 is roughly 3.3 mm2 — close to but not identical with a metric 4 mm^2 conductor.
What about aluminium wire?
Multiply the listed resistance by about 1.6 to account for aluminium's higher resistivity, and derate ampacity by roughly one gauge.