WaterCalculator

Water Pump Calculators

17 tools for sizing and running water pumps — horsepower and power draw, total dynamic head and NPSH, flow and run time, sizing by pump type, and the savings from a variable-speed drive. Each runs on the recognised standard formula, with the working shown.

John Mac, PE Curated and reviewed by John Mac, PE, Water Systems Specialist.

Power & horsepower

Pump Horsepower CalculatorHorsepower needed for a given flow and head. Pump Power CalculatorPower draw from a pump's flow, head and efficiency. Pump Energy CostRunning cost of a pump by power draw and rate.

Head (TDH, NPSH)

Total Dynamic HeadA pump's total dynamic head from static head and losses. Pump Head CalculatorHead a pump must produce for the system. NPSH CalculatorNet positive suction head, to check against cavitation.

Flow, run-time & efficiency

Pump Flow RateFlow rate a pump delivers at a given head. Pump Run TimeHow long a pump runs to move a given volume. Pump Efficiency CalculatorA pump's efficiency from input power and hydraulic output. Pump Cycle TimeTime between a pump's on and off cycles.

Sizing by type

Pump Sizing CalculatorSize a pump for your flow and head requirements. Booster Pump PressurePressure boost needed from a booster pump. Submersible Pump SizeSize a submersible pump for a well's depth and yield. Jet Pump SizeSize a jet pump for suction depth and flow. Circulator Pump SizingSize a circulator pump for a hydronic loop.

Affinity laws & savings

Pump Affinity LawsHow flow, head and power scale with pump speed. Variable-Speed Pump SavingsEnergy savings from a variable-speed pump drive.

About our pump calculators

These tools rest on the engineering math pump sizing is built on — the pump affinity laws for speed and impeller changes, net positive suction head (NPSH) theory to avoid cavitation, and standard motor horsepower and efficiency formulas. Every figure is verified against the live calculator, and each page lists its sources. For the full detail of how we build and check them, see our methodology.

Browse other categories

ScienceDensity, weight, heat and properties. FlowPipe flow, velocity, friction loss. PressureHead, PSI, depth and losses. UsageHousehold use, footprints, savings. CostBills, rates and running costs. TreatmentSoftening, filtration, chemistry. DrainageSlopes, drain sizing, stormwater.