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Calcimator

Pump Sizing Calculator

Size a centrifugal pump by calculating hydraulic horsepower, brake horsepower, motor size, NPSH required, and annual energy cost.

Inputs

GPM
ft
lb/ft³
%

Results

Brake Horsepower

1.68 HP

Motor Size

2 HP

Hydraulic Horsepower1.26 HP
NPSH Required (est.)7.5 ft
Annual Energy Cost$1,100
How to Use This Calculator
  1. Enter the Flow Rate in GPM required at the design operating point.
  2. Enter the Total Dynamic Head in ft — sum static lift, friction losses in piping, and any pressure differential required at the destination.
  3. Set the Fluid Density in lb/ft³: water at 60°F = 62.4 lb/ft³; adjust for other fluids.
  4. Set the Pump Efficiency %: small centrifugal pumps ≈ 50–70%, large centrifugal ≈ 75–90%.
  5. Review Brake Horsepower and the recommended Motor Size in HP — the motor should be the next standard size above BHP.
  6. Check the estimated NPSH Required in ft against the available NPSH at the pump suction to prevent cavitation.
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