Pump Equations Formulas Calculator

Fluid Mechanics and Hydraulics

Solving For Flow Rate or Discharge
Flow Rate or Discharge
Note: Equation for water at 68 Fahrenheit. Usually, temperature correction for water is negligible.


water horsepower (WHP)
total head (H)


water horsepower (WHP)
= 0
= 0
total head (H)
= 0
= 0


flow rate or discharge (Q)

Other Units:

Change Equation
Select to solve for a different unknown
Water Horsepower
water horsepowerSolve for water horsepower
flow rate or dischargeSolve for flow rate or discharge
total headSolve for total head
pump efficiencySolve for pump efficiency
brake horsepowerSolve for brake horsepower
Net Positive Suction Head and Cavitation
NPSH - net positive suction headSolve for NPSH - net positive suction head
fluid or liquid velocitySolve for fluid or liquid velocity
pressure at impeller inletSolve for pressure at impeller inlet
fluid or liquid vapor pressureSolve for fluid or liquid vapor pressure
specific weight of fluid or liquidSolve for specific weight of fluid or liquid
acceleration of gravitySolve for the acceleration of gravity
WHP=water horsepower
Q=flow rate or discharge
H=total head
n=pump efficiency
BHP=brake horsepower
NPSH=net positive suction head
V=velocity of fluid or liquid
p=impeller inlet pressure
pv=vapor pressure of fluid or liquid
SW=specific weight of fluid or liquid
g=acceleration of gravity

References - Books:
1) P. Aarne Vesilind, J. Jeffrey Peirce and Ruth F. Weiner. 1994. Environmental Engineering. Butterworth Heinemann. 3rd ed.

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