⚡ Pump Power Calculator
Calculate shaft power and motor power of a pump system.
⚡ Pump Power Calculator
📊 Result
Please enter values on the left and click calculate.
Calculator Description
The pump power calculator computes the power needed to move fluid through a pump system — the shaft power and the motor power. Based on flow, head, fluid density and efficiencies, it estimates the required energy so the right pump and motor can be selected.
Pump power calculation rests on variables such as flow rate, head, fluid density, pump efficiency and motor efficiency. Accurate sizing prevents both underperformance from undersizing and wasted cost/energy from oversizing.
This calculator computes the shaft power (the actual hydraulic power the pump imparts to the fluid) and the motor power (the total power the driving motor consumes), correctly accounting for efficiency losses at each stage.
Term Glossary
- Head
- The height a pump lifts or pushes fluid, expressed as a pressure head
- Flow rate
- The volume of fluid transferred per unit time
- Shaft power
- The actual power the pump needs to transfer fluid
- Motor power
- The total power consumed by the motor that drives the pump
Formula
Shaft Power
This is the hydraulic power required to lift fluid by head H and move it at flow Q. Multiplying density ρ and gravity g gives the rate of potential-energy gain; dividing by pump efficiency ηp yields the actual shaft power needed.
- ρ — Fluid density [kg/m³ or lb/ft³]
- g — Gravitational acceleration (9.81 m/s² or 32.174 ft/s²)
- H — Pump head [m or ft]
- Q — Flow rate [m³/s or gpm]
- ηp — Pump efficiency (decimal, 0–1)
Motor Power
This is the total power the motor consumes to deliver the shaft power to the pump. Divide by the motor efficiency ηm to obtain the required input electrical power.
- ηm — Motor efficiency (decimal, 0–1)
How the formula works
- Larger flow, head or density increases the required power linearly.
- Lower efficiency means more input power is needed for the same duty, so selecting high-efficiency pump and motor matters.
- The division by 1000 converts the W result (kg·m²/s³) to kW in the metric system.
Worked example
For water (ρ = 1000 kg/m³) lifted H = 20 m at Q = 0.05 m³/s with pump ηp = 0.75 and motor ηm = 0.9: hydraulic power = 1000 × 9.81 × 20 × 0.05 = 9810 W. Shaft power = 9810 / (0.75 × 1000) ≈ 13.08 kW, and motor power = 13.08 / 0.9 ≈ 14.53 kW.
Useful Tips
Efficiency Improvement Methods
- Proper Pump Selection: choose a pump that operates near its best-efficiency point (BEP) for the duty.
- Variable Frequency Drive (VFD): when flow adjustment is needed, VFD is more energy efficient than throttling valves.
- Piping Optimization: minimize friction losses by reducing unnecessary fittings and pipe length.
- Regular Maintenance: inspect impeller wear, seal wear, etc. to prevent efficiency loss.
Limitations & cautions
- This is a steady-state calculation using rated efficiency; real efficiency at part load can be lower.
- Friction/local losses, NPSH margin and starting torque must be checked separately.
- High-viscosity liquids (oils, etc.) sharply reduce efficiency and head, so water-based values should not be used directly.