Amps to Horsepower Calculator

Enter current, voltage, power factor, and phase to calculate the mechanical horsepower a motor draws from the electrical supply.

How to Use the Amps to Horsepower Calculator

Enter current, voltage, and power factor, then set Single-Phase or Three-Phase to match the motor's supply — horsepower recalculates immediately on every change, no separate button to press.

This calculator answers a question the plain Amps to kW tool can't: given a motor's electrical draw, what does that amount to in the unit its nameplate actually uses? Real power in kW is a fine intermediate figure, but nobody buys a "3.68 kW pump" — they buy a 5 HP one. Getting there means converting real power to mechanical units with the standard imperial constant:

Single-phase: HP = (V × I × PF) ÷ 745.7
Three-phase:  HP = (√3 × V × I × PF) ÷ 745.7

230V, 15A, and a 0.85 power factor on a single-phase circuit works out to 3.93 HP. Put the same current and power factor on a 400V three-phase supply instead and the figure jumps to 11.85 HP — three-phase distribution lets a given current at a given voltage carry roughly three times the load a single phase can, which is exactly why larger motors are wired three-phase almost without exception.

Electrical Horsepower Isn't the Same as Shaft Horsepower

This number describes the real electrical power flowing into the motor's windings — it is not the mechanical power actually available at the shaft. Every motor loses some of that input to heat, friction, and magnetic losses before anything reaches the output shaft; typical efficiency runs anywhere from about 75% for a small, cheap motor to over 95% for a large, well-designed industrial one. A motor drawing an electrical-equivalent 10 HP at 85% efficiency delivers roughly 8.5 HP of actual mechanical output, not 10. Treat this calculator's result as the electrical draw expressed in horsepower units, not a guaranteed output rating — check the nameplate's own HP figure, which already accounts for the manufacturer's measured efficiency, before sizing anything mechanical against it.

Working the other direction — starting from a known horsepower rating instead of a measured current — is the Horsepower to Amps calculator's job. And if torque and RPM are what you actually have on hand rather than anything electrical, the site's Horsepower Calculator converts those directly.