Wire Gauge / Electrical Load Calculator
Recommended AWG, load in watts and voltage drop.
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Recommended copper conductor
8 AWG
Ampacity 50 A at 75°C · 16,510 circular mils
Sizes assume copper conductors at 75°C in a normal ambient with no more than three current-carrying conductors in a raceway. Derate for heat, bundling, or aluminium.
8 AWG · 1.95% drop · 7.20 kW
How this is calculated
Conductor selection has to satisfy two separate limits. The first is ampacity: the conductor must safely carry the current without overheating, which comes from published tables for copper at a given insulation temperature rating. The second is voltage drop over the length of the run.
Vdrop = (2 × K × I × L) ÷ circular mils (single phase)
Vdrop = (√3 × K × I × L) ÷ circular mils (three phase)
K is the resistivity constant, about 12.9 ohm-circular-mils per foot for copper at 75°C. L is the one-way run length; the factor of 2 on a single-phase circuit accounts for current travelling out and back.
Load is calculated from voltage, current and power factor:
watts = V × I × PF (single phase) | watts = √3 × V × I × PF (three phase)
The recommendation shown is the smallest conductor that meets both the ampacity requirement and your voltage drop target. Always confirm against the current edition of your local electrical code, and derate for high ambient temperature, conduit fill, or aluminium conductors, which need roughly one to two sizes larger than copper for the same load.