How to Calculate GPM from PSI for Water

By Joshua Bush
Pumped from the streets into the river close up
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The flow rate of water in gallons per minute, or gpm, can be calculated with the help of the Bernoulli equation and careful unit conversion. If the pressure is known in pounds per square inch, or psi, at two locations along the pipe, then the Bernoulli equation can be used to determine the velocity of the water. The Bernoulli equation states that velocity is determined by calculating difference in pressure between two points, multiplying by 2, dividing by the density of water and then taking the square root. You then get the flow rate by multiplying the velocity by the cross-sectional area of the pipe.

About the Author

Joshua Bush has been writing from Charlottesville, Va., since 2006, specializing in science and culture. He has authored several articles in peer-reviewed science journals in the field of tissue engineering. Bush holds a Ph.D. in chemical engineering from Texas A&M University.