KEVOS® MAKEOS · Hydraulics
Pump Shaft Power
What shaft power does a pump need for this flow and head?
Calculate the hydraulic power delivered to a liquid and the shaft power a pump needs at a given flow, head and efficiency.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Pump flow | L/min | Flow at the duty point. |
| Total dynamic head | m | Total dynamic head the pump must develop at that flow, including static lift and losses. |
| Liquid density | kg/m³ | Liquid density at the pumping temperature. |
| Overall pump efficiency (as a fraction) | fraction 0–1 | Pump efficiency as a fraction from 0.01 to 1, read from the pump curve at the duty point. Enter 0.7 for 70%. |
Method and formulas
- Hydraulic power (kW) = ρ × g × Q × H / 1,000, with Q in m³/s (L/min ÷ 60,000) and g = 9.80665 m/s².
- Shaft power = hydraulic power / efficiency.
- Example: 120 L/min, 30 m, 1,000 kg/m³ and efficiency 0.7 give a hydraulic power of 0.588399 kW and a shaft power of 0.840570 kW.
Limitations
- Efficiency varies along the pump curve; the result applies only at the entered duty point.
- Motor losses, drive losses and the motor sizing margin are not included. Viscous liquids need viscosity corrections to the pump curve.
- No certification or pump selection is implied.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Estimate pump input power at a duty point
- Compare duty points or pump efficiencies
- Check a motor size before supplier selection
Who it is for
- Design engineers
- Maintenance engineers
What you get
- Pump shaft power (kW)
- Hydraulic power (kW)
Interpreting the result
- Size the motor for the highest shaft power over the operating range, not only the normal duty point.
Before relying on the result
- Read efficiency and power from the manufacturer’s pump curve for the actual impeller and speed.
- Apply the pump or motor manufacturer’s sizing allowance before choosing a motor.
References
- US Department of Energy, DOE-HDBK-1012/3-92, Fluid Flow — https://www.energy.gov/sites/default/files/2026-04/DOE-HDBK-1012-92_VOL3.pdf
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 365–368. Topic reference; no source tables or recommended settings are reproduced.
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