Wire Gauge Ampacity Calculator (AWG)

About this calculator

Ampacity is the maximum current a wire can carry continuously without exceeding its insulation's safe temperature rating, and in the U.S. it's governed by NEC Table 310.16, which lists safe amperage by copper (or aluminum) wire gauge (AWG) and insulation temperature class — 60°C, 75°C, or 90°C. A thicker wire (lower AWG number) and higher-rated insulation both allow more current; for example, 12 AWG copper is rated for 20A at 60°C but up to 30A at 90°C insulation, though the lower figure is typically what's used for circuit breaker sizing.

Electricians, electrical contractors, and DIYers wiring a panel, outlet circuit, or extension cord reference ampacity tables constantly to choose wire gauge that won't overheat under expected load, since undersized wire is a fire hazard and a common code violation.

This calculator looks up the NEC-rated ampacity for a chosen AWG size and insulation temperature rating, giving a quick reference without flipping through the full NEC table by hand.