Use this form for calculating the Hydraulic (fluid power) horsepower.
Formula: HP = PSI * GPM / 1714
PSI is gauge pressure in pounds per square inch; GPM is oil flow in gallons per minutes.
Horsepower for driving a pump: For every 1 HP of drive, the equivalent of 1 GPM @ 1500 PSI can be produced.
Horsepower for idling a pump: To idle a pump when it is unloaded will require about 5% of its full rated horsepower.