Wire Gauge Calculator
Choosing the correct wire gauge is critical for electrical safety and performance. Undersized wire causes excessive voltage drop, wasted energy, overheating, and potential fire hazards. This calculator determines the proper AWG wire size based on circuit amperage, voltage, distance, and acceptable voltage drop for copper and aluminum conductors.
Wire sizing must satisfy two requirements: ampacity (current-carrying capacity without overheating) and voltage drop (signal loss over distance). The NEC (National Electrical Code) sets ampacity limits for each gauge in various installation conditions. Voltage drop is calculated as Vd = 2 × L × I × R / 1000, where L is the one-way distance in feet, I is current in amps, and R is resistance per 1,000 feet.
The NEC recommends maximum 3% voltage drop for branch circuits and 5% total voltage drop from the service entrance to the furthest outlet. Long wire runs to detached garages, workshops, or barn buildings often require upsizing the wire gauge to stay within voltage drop limits, even when the ampacity of a smaller wire would be sufficient.
Copper wire is standard for most residential and commercial applications. Aluminum wire costs less per foot and is commonly used for large feeder circuits (100A+ service entrances, sub-panels) where the weight and cost savings are significant. Aluminum requires special connectors rated for aluminum and should never be connected to devices rated for copper only.