Recommend a copper wire gauge (AWG) based on amperage, one-way run length, and acceptable voltage drop.
Wire Gauge
— copper
Minimum for the target drop.Usage Tip
Voltage drop adds up on long runs; upsizing one gauge is cheap insurance against dimming lights and humming motors.
THE MATH
circular mils = (2 × K × amps × length) ÷ voltage drop
K (copper) = 12.9, voltage drop = drop % × 120 V
K (copper) = 12.9, voltage drop = drop % × 120 V
Long wire runs lose voltage. To keep the drop within a target, the conductor must have enough cross-section, measured in circular mils, which maps to a wire gauge.
Enter the load amps, the one-way run length, and an acceptable voltage drop (3 percent is common).
Sizing assumes a 120 V copper circuit; also confirm the gauge meets ampacity for the breaker.
Sizing assumes a 120 V copper circuit; also confirm the gauge meets ampacity for the breaker.