Pump Power & Horsepower Calculator
Calculate hydraulic power, shaft power, motor load, and energy cost for centrifugal and positive displacement pumps. Essential for pump sizing and motor selection in chemical process plants.
⚙️ Pump Power Calculator
Use this calculator to determine the hydraulic power (power delivered to the fluid), shaft power (power required at the pump shaft), and motor input power for any pumping application. The calculator supports both metric (kW) and imperial (HP) units.
Phyd = Q × H × SG / 3960 (US: HP, with Q in GPM, H in ft)
Shaft Power: Pshaft = Phyd / ηpump
Motor Power: Pmotor = Pshaft / ηmotor / ηdrive
Enter Pump Operating Conditions
📊 Pump Power Results
Understanding Pump Power Calculations
Hydraulic power (also called water horsepower) is the power actually transferred to the fluid. It depends only on flow rate, head, and fluid density — not on pump efficiency.
Shaft power (brake horsepower) is the power that must be delivered to the pump shaft. It accounts for internal pump losses (hydraulic, volumetric, mechanical). Always larger than hydraulic power.
Motor input power is the electrical power drawn from the supply. It includes motor and drive losses.
Typical Pump Efficiencies
| Pump Type | Typical Efficiency | Best Efficiency Point (BEP) |
|---|---|---|
| Small centrifugal (< 5 kW) | 30–50% | Varies widely |
| Medium centrifugal (5–50 kW) | 55–75% | Near BEP |
| Large centrifugal (> 50 kW) | 75–90% | Well-defined BEP |
| Positive displacement (reciprocating) | 80–95% | High at design point |
| Gear pump | 60–80% | Viscosity dependent |
| Progressive cavity | 50–70% | Speed dependent |
Frequently Asked Questions
TDH is the total equivalent height that a fluid must be pumped, including static lift (elevation difference), pressure difference between suction and discharge, and all friction losses in pipes, fittings, and equipment. TDH = H_static + H_pressure + H_friction.
1 HP (mechanical) = 0.7457 kW. 1 kW = 1.341 HP. For electrical HP, 1 eHP = 0.746 kW.
Always select a motor with a service factor margin. Typically, the motor nameplate rating should be 10–25% above the maximum expected shaft power. API 610 requires at least 10% margin for pumps up to 25 kW, and specific margins for larger sizes.
Net Positive Suction Head (NPSH) is the margin above vapor pressure available at the pump suction. Available NPSH (NPSHa) must exceed the pump's required NPSH (NPSHr) to prevent cavitation, which damages the impeller and reduces performance.
Higher viscosity reduces pump efficiency and head generation. Centrifugal pumps are generally limited to fluids below ~1000 cP. For viscous fluids, use positive displacement pumps or apply Hydraulic Institute viscosity correction charts.