Pump System Curve and Operating Point — online
System curve from one known point or from the pipe, the operating point for 1–4 pumps in parallel or series, and throttle vs VFD vs impeller trim to a target flow, with the yearly energy cost.
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 29) — the Guide, method and references are in the Excel file.
What this pump system curve and operating point calculator does
See where your pump really runs — and what controlling it the wrong way costs. System curve from one known point or from the pipe, the operating point for 1–4 pumps in parallel or series, and throttle vs VFD vs impeller trim to a target flow, with the yearly energy cost.
- System curve two ways. Static head plus K·Q² from one known point, or a pipeline by Darcy with Swamee–Jain friction and fittings.
- Operating point. Flow, head, efficiency, power and % of BEP for 1 to 4 pumps, in parallel or in series; what happens when one pump trips.
- Flow control compared. Throttle valve, VFD speed and trimmed diameter to reach a target flow, with shaft and electrical power.
- Energy cost. Yearly cost of each option and the VFD saving, with motor and VFD efficiencies.
- Charts. Pump and system curves with the operating point, and a power comparison bar chart.
- Same liquid list. 54 pumped liquids, mixtures or your own properties.
What you enter
- Pumps running together
- System curve
- 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
- Specific heat
- Mixture composition in
- Mixture
What you get
- Static head (elevation + pressure difference)
- Operating flow (total)
- Operating head (system)
- Flow per pump
- Flow per pump as % of BEP
- Pump efficiency
- Shaft power per pump
- Shaft power, all pumps running
- Shut-off head of the pumps running
- If one pump trips: flow of the remaining pumps
- If one pump trips: flow per remaining pump as % of BEP
- System head at the target flow
- Throttling: head burnt in the control valve
- Throttling: shaft power (all pumps)
How it was checked
Operating points for 1 pump, 2 in parallel, 2 in series and a pipeline system match an independent Python model; VFD speed and trim diameters identical.
Related
- Free quick calculator — a simpler free version for a fast estimate.
- Calculation guide — the equations behind this tool, with a worked example.
- Pump System Curve and Operating Point Excel tool — USD 29, keep the workbook and its Guide.
- All 40 online tools
Questions
Is the pump system curve and operating point 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 System Curve and Operating Point 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.