Formula
Three-phase: Amps = (HP × 746) ÷ (Volts × 1.732 × Eff × PF)
1 electric horsepower equals exactly 746 watts. Because electric motors are not 100% efficient and AC power involves a power factor, the actual electrical power drawn is higher than the mechanical power output.
Worked Example
This calculator provides estimates based on standard mathematical formulas. Real-world results will vary based on mechanical condition, environmental factors, and other variables.
Frequently Asked Questions
Power factor is the ratio of working power (true power) to apparent power in an AC circuit. It reflects how effectively the electrical power is being converted into useful work.
For three-phase: Amps = (HP × 746) ÷ (Volts × √3 × power factor × efficiency). For single-phase, drop the √3. Enter your values to get the exact current.
Motors aren't 100% efficient and draw reactive current, so power factor and efficiency convert the ideal power into the real current the motor pulls from the supply.
Roughly 4–5 amps, depending on the motor's efficiency and power factor. The calculator gives a precise figure for your specific motor.
No. DC uses Amps = (HP × 746) ÷ (Volts × efficiency) with no power factor or √3 term, since DC has no phase or reactive component.