Motor Full-Load Current Calculator

About this calculator

Full-load current (FLC) is the current an AC motor draws when delivering its rated horsepower at rated voltage — the number stamped on the nameplate and used to size breakers, overload relays, and conductor gauge. This calculator derives it from the motor's power, voltage, power factor, and efficiency rather than reading it off a lookup table.

For a single-phase motor, I = P / (V × PF × η); for three-phase, I = P / (√3 × V × PF × η), where P is output power in watts, V is line voltage, PF is power factor, and η is efficiency (motor input power is always higher than its mechanical output). The √3 factor accounts for the phase relationship between the three line currents in a balanced three-phase system.

Electricians and electrical engineers use full-load current to select the correct wire ampacity per NEC/IEC tables, set thermal overload protection at roughly 115–125% of FLC, and confirm a motor won't nuisance-trip a breaker sized too close to its running current.