Pump Head, Power and Efficiency — online
Head, efficiency and power curves for any impeller diameter and speed from the vendor's curves, the motor size with API 610 margins, low-flow alerts and a field test against the curve.
Yellow cells are inputs; orange cells are choices; blue cells choose the unit. Select or hover over an input to see its help in the box below the toolbar. The sheet is the same as the Excel tool (USD 39) — the Guide, method and references are in the Excel file.
What this pump head, power and efficiency calculator does
Vendors draw a few impellers. This tool draws the one you actually have — and tells you what it costs to run. Head, efficiency and power curves for any impeller diameter and speed from the vendor's curves, the motor size with API 610 margins, low-flow alerts and a field test against the curve.
- Curves for any impeller. Head, efficiency and power curves for any diameter and speed, blended from up to four vendor curves; the existing curves and the new one drawn together, with drop lines to the duty point.
- Motor sizing. Shaft power at duty and at the end of the curve; motor rating with API 610 margins or non-overloading, rounded to standard IEC sizes.
- Design checks. Head margin, trim diameter or VFD speed that meets the duty, throttling loss and its yearly cost.
- Low-flow alerts. Minimum stable and thermal flow screening, % of BEP, temperature rise — with plain-language warnings for oversized pumps.
- Field test. Total head, efficiency and wire-to-water efficiency from gauges and motor power, corrected to curve speed, with the efficiency gap in kW and money.
- 54 pumped liquids. Built-in pump liquid list with vapour-pressure checks, mixtures of up to 8 liquids, or your own properties.
What you enter
- Evaluation
- Flow
- Head from
- Power from
- Motor sizing
- Liquid data
- Liquid
- Pumping temperature
- Concentration (% by mass)
- Watson characterisation factor K
- Kinematic viscosity at 40 °C
- Kinematic viscosity at 100 °C
- Density at the pumping temperature
- Viscosity at the pumping temperature
What you get
- Impeller diameter and speed
- Shut-off head (zero flow)
- Best efficiency point (BEP) flow
- Head at BEP
- Efficiency at BEP
- End of the curve (last vendor point)
- Shaft power at the end of the curve (maximum)
- Preferred operating region — from
- Preferred operating region — to
- Minimum continuous stable flow (MCSF)
- Thermal minimum flow
- Minimum flow used for the checks
- Kinematic viscosity
- Specific speed at BEP, Ns (US: rpm, gpm, ft)
How it was checked
An independent Python model gives the same head, efficiency, power, trim and VFD results for interpolated and extrapolated impellers (4+ significant figures); field test reproduces the free web calculator.
Related
- Free quick calculator — a simpler free version for a fast estimate.
- Calculation guide — the equations behind this tool, with a worked example.
- Pump Head, Power and Efficiency Excel tool — USD 39, keep the workbook and its Guide.
- All 40 online tools
Questions
Is the pump head, power and efficiency calculator free?
You can enter and check all your data free. The full results, findings and printable sheet are unlocked with a 3-run pack (USD 9), a monthly subscription to all 40 online tools (USD 15) or a yearly one (USD 99).
Are the results the same as the Excel tool?
Yes. The online tool runs the formulas of the Pump Head, Power and Efficiency Excel workbook, checked cell by cell against the Excel file.
Which units can I use?
SI, US customary and British units — choose the unit next to each input.