Free Pump Power Calculator
Determine the power required to drive a pump for a given flow rate and total head.
L/s
m
kg/m^3
%
Required Shaft Power
7.85 kW
Hydraulic Power5.89 kW
Required Shaft Power vs Flow Rate (Q)
Pump Power Calculation
The power a pump must supply depends on the flow rate, the head it must overcome, and pump efficiency.
Formulas
Hydraulic power = rho g Q H (useful work on the fluid)
Shaft power = rho g Q H / eta (actual input from motor)
where rho is fluid density, g = 9.81 m/s^2, Q is volumetric flow rate, H is total dynamic head, and eta is pump efficiency.
Example Calculation
A pump delivers 20 L/s of water against 30 m total head at 75% efficiency.
- 01Q = 20 L/s = 0.020 m^3/s
- 02Hydraulic power = 1000 x 9.81 x 0.020 x 30 = 5886 W = 5.89 kW
- 03Shaft power = 5.89 / 0.75 = 7.85 kW
- 04Select a motor of at least 7.5 kW (next standard size up).
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