HP Calculator   PSI :   GPM:     HP   =    _________

Formula: HP = PSI * GPM / 1714 PSI is gauge pressure in pounds per square inch; GPM is oil flow in gallons per minutes. Rules-Of-Thumb: 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.