Water / Pump Horsepower Calculator

STEP BY STEP

How to use water / pump horsepower calculator

1. Check the input units and assumptions.
2. Review the result and example.

IN PRACTICE

Example

At 100 GPM, 100 ft of total head, SG = 1.0: hydraulic HP = 100 × 100 ÷ 3,960 = 2.53 HP. At 75% pump efficiency, brake HP = 2.53 ÷ 0.75 = 3.37 HP. Motor selection needs its own margin and motor-efficiency check.

GOOD TO KNOW

Which assumptions should I check?

Efficiency changes across the pump curve. Do not assume the best-efficiency-point value applies everywhere. Brake horsepower is not the same as electrical input power; motor and drive losses add more input. NPSH, cavitation, pipe losses and motor sizing remain separate checks.