Formula Used
How to Use This Calculator
- Select a calculation mode.
- Enter flow, head, pressure, or known power.
- Choose a fluid preset.
- Confirm efficiency assumptions.
- Enable the TDH builder when needed.
- Enter pipe and fitting data.
- Add electrical and cost information.
- Enable NPSH or affinity checks.
- Review warnings and calculated results.
- Export a CSV or printable report.
Example Data Table
| Application | Flow | Head | Pump Efficiency | Approximate Hydraulic Power |
|---|---|---|---|---|
| Small water transfer | 10 m³/h | 15 m | 60% | 0.41 kW |
| Building booster | 30 m³/h | 35 m | 70% | 2.86 kW |
| Irrigation main | 80 m³/h | 45 m | 75% | 9.81 kW |
| Industrial transfer | 150 m³/h | 60 m | 78% | 24.52 kW |
| High-rise service | 200 m³/h | 100 m | 82% | 54.48 kW |
Understanding Pump Power
Hydraulic Output
Hydraulic power describes useful energy delivered to the moving fluid. Flow and total head determine this value. Fluid density also changes power demand. Denser liquids require greater power at equal duty. Gravity remains nearly constant for normal terrestrial installations.
Shaft and Electrical Demand
The pump cannot convert every input watt. Internal leakage, turbulence, bearings, and seals create losses. Shaft power therefore exceeds hydraulic output. Motor and drive losses increase electrical demand further. Use realistic efficiency values from current manufacturer data.
Total Dynamic Head
Total dynamic head combines every required head component. Static head reflects elevation differences. Pressure head represents vessel or terminal pressure. Velocity head describes changing liquid speed. Friction head covers pipes, valves, fittings, and entrances.
Pipe Friction
Darcy–Weisbach supports many fluids and operating conditions. It uses velocity, diameter, roughness, and Reynolds number. Hazen–Williams is commonly used for water systems. Its coefficient depends on pipe material and condition. Old pipes can create much larger losses.
Motor Selection
Calculated shaft power is not the final motor rating. Designers usually add a suitable margin. They also inspect the full pump curve. Maximum absorbed power may occur away from duty. Starting torque can affect the final selection.
Electrical Current
Current depends on voltage, phase, and power factor. Three-phase systems use the square-root-three relationship. Actual nameplate current may differ from estimates. Motor efficiency also varies with load. Always confirm conductor and protection requirements locally.
Energy Cost
Small efficiency changes can create large yearly savings. Long operating schedules magnify every loss. The calculator estimates energy from input power. It then applies operating hours and electricity price. Cost per volume supports practical system comparisons.
Variable-Speed Operation
Pump affinity laws estimate centrifugal pump speed effects. Flow changes approximately with speed. Head changes with speed squared. Power changes with speed cubed. Real systems may depart from these simplified relationships.
NPSH Protection
NPSH checks help identify cavitation risk. Available NPSH depends on atmospheric pressure and suction conditions. Vapor pressure reduces the available margin. Suction friction also lowers available head. Required NPSH comes from the pump manufacturer.
Practical Verification
Use calculations for screening and design comparison. Confirm fluid properties at operating temperature. Review the actual pump and system curves. Check minimum and maximum operating limits. Final equipment selection needs qualified engineering review.
Duty Point Review
A pump operates where curves meet. This intersection determines actual flow and developed head. Valves and pipework changes move the system curve. Speed or impeller changes move the pump curve. Efficient selections operate near the best efficiency point. Poor duty points increase vibration and maintenance.
Data Quality
Measured data requires calibrated instruments and stable conditions. Record suction pressure, discharge pressure, flow, voltage, and current. Temperature matters because liquid properties can change. Repeat measurements before accepting unusual efficiency results. Compare calculated power with motor nameplate information. Document every assumption for engineering review.
Reliable inputs always produce safer pump and motor selections.