Construction & Home
Wire Gauge (AWG)
Updated 2025-07-21
Definition
The American Wire Gauge standard for electrical conductor diameter. Lower numbers mean thicker wire and higher current capacity. The National Electrical Code ampacity table assigns 15-amp circuits to 14 AWG copper, 20-amp to 12 AWG, 30-amp to 10 AWG, and 40-amp to 8 AWG for standard 60°C insulation. Voltage drop over distance is the second gauge driver: a 20-amp circuit running 100 ft requires upsizing to 10 AWG to keep voltage drop under the NEC recommended 3%. Undersized wiring is a leading cause of residential fires.
Primary source: NFPA 70 National Electrical Code
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