Calculate your pump's hydraulic horsepower and shaft (brake) horsepower by entering Flow Rate (GPM), Pressure (PSI), and Pump Efficiency (%). Results show both hydraulic HP and the motor HP required to drive the pump, accounting for efficiency losses.
Motor HP Required
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Hydraulic Horsepower
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Brake (Shaft) Horsepower
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Hydraulic Power (kW)
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Power Lost to Inefficiency
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Hydraulic horsepower (HHP) is calculated as: HHP = (GPM × PSI) / 1714. This represents the theoretical power transferred to the fluid, ignoring any mechanical or volumetric losses inside the pump itself.
Hydraulic horsepower is the power actually delivered to the fluid. Brake horsepower (BHP) — also called shaft horsepower — is the power required at the pump shaft, accounting for the pump's internal efficiency. BHP = HHP / pump efficiency. Since no pump is 100% efficient, BHP is always higher than HHP.
The electric motor driving the pump also has losses. The total motor HP required is BHP divided by motor efficiency. For example, if your pump needs 10 BHP and your motor is 90% efficient, you need an 11.1 HP motor. Undersizing the motor leads to overheating and premature failure.
A reasonable default for most centrifugal pumps is 75–85%. Industrial pumps in optimal conditions can reach 90%. Smaller or older pumps may be closer to 60–70%. If your pump manufacturer provides a performance curve, use the efficiency at your operating point.
Pump horsepower scales directly with the specific gravity of the fluid. Pumping a fluid denser than water (SG > 1) requires proportionally more power, while a lighter fluid (SG < 1) requires less. Always adjust for specific gravity when pumping anything other than water.
You can measure flow rate with a flow meter installed in the pipe, or estimate it from the pump's performance curve at your operating head. For irrigation systems, the total nozzle or emitter output ratings can be summed to estimate GPM. Knowing pipe diameter and velocity also allows calculation: GPM = velocity (ft/s) × pipe area (ft²) × 448.83.
The constant 1714 comes from unit conversion: 1 horsepower = 550 ft·lbf/s, and combining the conversion factors for gallons-per-minute to ft³/s and PSI to lbf/ft² yields the constant 1714. It only applies when flow is in GPM and pressure is in PSI.
Yes. The formula GPM × PSI / 1714 applies to any hydraulic pump regardless of fluid type. For fluids other than water, enter the correct specific gravity to get accurate power figures. This is commonly used for hydraulic power units, mobile equipment hydraulics, and industrial machinery.