Pump Power Calculator
Estimate hydraulic and pump shaft power at a stated flow, total head, liquid density and pump efficiency.
Use the Pump Power Calculator
Estimate hydraulic and pump shaft power at a stated flow, total head, liquid density and pump efficiency.
Calculations happen locally in your browser. ToolLott does not send these inputs to a server for this tool.
Preliminary engineering screening only. It does not replace project-specific design, applicable codes/standards, manufacturer data, transient/fatigue studies, geotechnical or site assessment, professional review or independent verification.
How to use it
Replace the worked-example values with actual project data. Review the intermediate quantities and visible assumptions before using the result elsewhere.
How the Pump Power Calculator works
Estimate hydraulic and pump shaft power at a stated flow, total head, liquid density and pump efficiency. The methodology below exposes the production equation, a QA-verified worked example and the boundary between this screen and detailed design.
Calculation breakdown
ToolLott will explain the current inputs and displayed result here.
Hydraulic and shaft power
The production engine evaluates P_hyd = rho g Q H; P_shaft = P_hyd / eta. It begins by convert flow from L/s to m³/s and efficiency to a decimal., then calculate hydraulic power from density, gravity, flow and head., and finally divide by pump efficiency for estimated shaft power. This keeps the calculation auditable instead of hiding design assumptions behind a single number.
P_hyd = rho g Q H; P_shaft = P_hyd / etaToolLott evaluates the relationship using the entered units and full numeric precision before display rounding.
| Symbol / input | Meaning | Unit |
|---|---|---|
flow | Flow rate (L/s) | user input |
head | Total dynamic head (m) | user input |
density | Liquid density (kg/m3) | user input |
efficiency | Pump efficiency (%) | user input |
Step-by-step method
- Convert flow from L/s to m³/s and efficiency to a decimal.
- Calculate hydraulic power from density, gravity, flow and head.
- Divide by pump efficiency for estimated shaft power.
Worked example
Alex, a project engineer, has a duty point of 40 L/s at 32 m head and an assumed pump efficiency of 75% and wants a shaft-power estimate.
Example inputs
- Flow rate (L/s): 40
- Total dynamic head (m): 32
- Liquid density (kg/m3): 998
- Pump efficiency (%): 75
Calculation / processing
Hydraulic power = 998 x 9.80665 x 0.04 x 32 / 1000 = 12.53 kW.Shaft power = 12.53 / 0.75.Estimated shaft power = 16.7 kW.
Use the result as a screening or quantity-planning value and compare it with the project criteria, manufacturer data and applicable engineering requirements before making a design or procurement decision.
Assumptions
- The entered values are representative of the condition being screened and use the units shown on the page.
- The equation models only the stated relationship; omitted system effects are not silently estimated.
Limitations
- This page is not engineering certification and does not replace applicable standards, design loads, manufacturer data, site investigation or competent professional review.
- Results can change materially when real geometry, losses, transients, material properties, duty cycles, safety factors or regulatory criteria differ from the simplified inputs.
Common questions
Is this a final engineering design?
No. It is a transparent screening calculation using the entered assumptions and the stated equation.
Why does the page show assumptions and limitations?
Engineering formulas are only valid within their modelling assumptions; exposing them helps users decide what additional design checks are required.
Should I use the rounded displayed value in later design work?
Use suitable calculation precision and the governing project/standard requirements rather than relying on display rounding alone.
Methodology sources
Related ToolLott tools
A realistic way Alex could use this tool
Alex is a project engineer.
Alex has a duty point of 40 L/s at 32 m head and an assumed pump efficiency of 75% and wants a shaft-power estimate.
Alex runs the example with flow = 40; head = 32; density = 998; efficiency = 75. Processing that specific set gives Estimated pump shaft power: 16.7 kW, making the result reproducible instead of relying on a generic claim about what the tool should do.
For this scenario, Estimated pump shaft power: 16.7 kW. Alex can use that specific result to estimate hydraulic and pump shaft power at a stated flow, total head, liquid density and pump efficiency, while keeping the stated assumptions separate from the calculation itself. The page also keeps this limitation explicit: Preliminary screening/planning calculation only.
Fictional scenario using realistic example data. For Ready tools, the worked result is tied to the tested example shown in the tool. Replace the figures with your own inputs and independently verify important professional, financial, legal, health or safety decisions.
What this calculator is for
Use it to estimate hydraulic and pump shaft power at a stated flow, total head, liquid density and pump efficiency.
It sits within ToolLott’s Hydraulic collection, where you can also calculate NPSH, pipe friction loss, pipe velocity, pump head, pump power, reservoir capacity and water-hammer screening values.