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Pump head & power
Enter the flow, the head you are pumping against and what you are pumping. The calculator returns hydraulic, shaft and motor input power, the motor frame to specify, and what it costs to run.
Your figures
Static lift plus friction losses plus any pressure at the destination.
Water 1000, vegetable oil 910, milk 1030, 50% caustic 1520.
65–80% for a well-selected centrifugal; lower at the ends of its curve.
Result
Power
- Hydraulic power
- 4.09 kW
- Shaft power
- 5.84 kW
- Motor input power
- 6.34 kW
- Motor frame
- 7.5 kW
ρ g Q H — the work actually done on the fluid
Hydraulic ÷ 70% pump efficiency
Shaft ÷ 92% motor efficiency
Next IEC size above the duty with 15% margin
Duty
- Differential pressure
- 2.94 bar
- Flow
- 50 m³/h · 13.89 litre/s
- Specific energy
- 0.127 kWh/m³
ρ g H
What it costs to move a cubic metre
Running cost basis
- Per 24 hours
- 152.3 kWh
- Per 30 days
- 4,568 kWh
Continuous running
Motor input power, not shaft power — the meter reads what the motor draws.
Questions
What counts as total head?
Static lift, plus every friction loss between suction and discharge, plus any pressure the destination is already at. Friction is the part most often forgotten — the pipe pressure drop calculator gives you that figure to add in.
Why three power figures?
They are three different things. Hydraulic power is the work actually done on the fluid. Shaft power is what the motor has to deliver, after pump inefficiency. Motor input power is what the meter reads, after motor inefficiency. Specify the motor on the third, cost the running on the third, and check the coupling on the second.
Why is there a margin on the motor frame?
Fifteen percent, because a pump that ends up running further down its curve than designed draws more power, not less, and a motor tripping on overload at commissioning is an expensive way to discover it.
Does this cover viscous liquids?
Only through density. A genuinely viscous fluid — heavy oil, molasses — derates both head and efficiency, and needs the supplier's viscosity correction charts. For water-like liquids the figures here are sound.