Pump Power Calculator
Enter the flow rate and head, plus the fluid density and pump efficiency. The calculator returns the hydraulic power delivered to the fluid and the shaft power the pump must draw.
How to calculate pump power
- Enter the volumetric flow rate in cubic metres per second.
- Enter the pump head in metres.
- Set the fluid density (default water) and the pump efficiency.
- Read the hydraulic power and shaft power in watts and kilowatts.
Examples
Water pump, ideal
Q = 0.05 m3/s, head = 20 m, density = 1000
hydraulic power = 9806.65 W (9.80665 kW)
At 70% efficiency
same duty, efficiency = 0.7
shaft power = 14009.5 W (about 14.01 kW)
Frequently asked questions
What is the pump power formula?
Hydraulic power equals density times g times flow rate times head. Shaft power is that hydraulic power divided by the pump efficiency.
What is the difference between hydraulic and shaft power?
Hydraulic power is the useful power added to the fluid. Shaft power is the larger input power the motor must supply because of losses.
What efficiency should I use?
Use the manufacturer's value where possible. Many centrifugal pumps fall between 0.6 and 0.85. The default of 1 gives the ideal hydraulic power.
What units does the calculator use?
Inputs are SI: cubic metres per second for flow, metres for head, kg/m3 for density. Power is shown in watts and kilowatts.
How do I get flow rate from litres per minute?
Divide litres per minute by 60000 to get cubic metres per second. For example, 3000 L/min is 0.05 m3/s.
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