How to Convert Motor HP to Amps

Electric motors are often rated in Horsepower (HP), but to size the wire, circuit breaker, or starter, you need to know the current in Amps (A).

The conversion isn't direct because you must account for the motor's Efficiency and Power Factor (for AC motors).

Step 1: Convert HP to Watts

First, convert the mechanical output power (HP) to electrical power (Watts).

1 HP (Electrical) = 746 Watts

Step 2: Apply the Formula

Depending on your power source, use one of the following formulas. Note that "Efficiency" and "Power Factor" should be used as decimals (e.g., 90% = 0.9).

DC Motors

Amps = (HP × 746) / (Volts × Efficiency)

AC Single-Phase Motors

Amps = (HP × 746) / (Volts × Efficiency × Power Factor)

AC Three-Phase Motors

Amps = (HP × 746) / (Volts × Efficiency × Power Factor × √3)

Typical Motor Full-Load Amps (FLA)

Approximate values for 230V Single-Phase AC Motors:

Horsepower	Approx. Amps (115V)	Approx. Amps (230V)
1/2 HP	9.8 A	4.9 A
1 HP	16 A	8 A
2 HP	24 A	12 A
5 HP	56 A	28 A

*Values are estimates based on NEC Table 430.248. Always check the motor nameplate.

Horsepower to Amps Calculator