Diameter, cross-section area, and resistance for every American Wire Gauge size — with typical copper amp capacity. Enter the current you need and it sizes the wire for you.
Sizing uses copper, NEC 60 °C. For a long run, go one size heavier to hold voltage drop under 3%. Aluminum wire carries roughly one gauge less than copper.
| AWG ▲ | Ø mm | Ø inch | Area mm² | Ω / 1000 ft | Amps (Cu, 60°C) |
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Diameter, area and resistance are computed from the AWG definition (Ø = 0.005·92^((36−n)/39) in) and copper resistivity. Amps are the NEC 60 °C copper figure where a building-wire rating exists; finer gauges (—) are signal/chassis wire, not rated for branch circuits.
12 AWG copper (rated 20 A at 60 °C). 14 AWG tops out at 15 A, so a 20 A circuit needs 12 AWG minimum. For long runs, step up to 10 AWG to limit voltage drop.
20 A as standard copper building wire (NEC 60 °C). The 75 °C and 90 °C insulation columns allow more, but breaker and terminal ratings usually hold you to 20 A on a 12 AWG branch.
Thinner. The gauge number goes up as the wire gets smaller — 14 AWG is thinner than 10 AWG. Below 1 AWG the scale continues as 1/0, 2/0, 3/0, 4/0 (said "one-aught," etc.), each larger than the last.
Resistance adds up over distance, dropping voltage and heating the wire. A gauge that's fine for a 10 ft run can sag badly over 100 ft. For long runs, size up so voltage drop stays under ~3%.