Pump Equations and Formulas Calculator

Fluid Mechanics and Hydraulics

Solving For Water Horsepower
Water Horsepower
Note: Equation for water at 68 Fahrenheit. Usually, temperature correction for water is negligible.


discharge or flow rate (Q)
total head (H)


discharge or flow rate (Q)
= 0
= 0
total head (H)
= 0
= 0


water horsepower (WHP)

Other Units:

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Select an equation to solve for a different unknown

Water Horsepower
water horsepower Solve for water horsepower
flow rate or discharge Solve for flow rate or discharge
total head Solve for total head
pump efficiency Solve for pump efficiency
brake horsepower Solve for brake horsepower

Net Positive Suction Head and Cavitation
NPSH - net positive suction head Solve for NPSH - net positive suction head
fluid or liquid velocity Solve for fluid or liquid velocity
pressure at impeller inlet Solve for pressure at impeller inlet
fluid or liquid vapor pressure Solve for fluid or liquid vapor pressure
specific weight of fluid or liquid Solve for specific weight of fluid or liquid
acceleration of gravity Solve 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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