PSI to GPM Calculator
Convert psito gpmcalculator between units instantly. Includes conversion tables, common equivalents, and calculation formulas.
Reviewed by Manoj Kumar, Mathematics Educator
Formula
GPM = Cd x A x sqrt(2 x g x h) x 448.831
This calculator uses the orifice flow equation. Pressure in PSI is first converted to head in feet (h = PSI x 2.31). The orifice area A is calculated from the diameter. The discharge coefficient Cd accounts for flow losses. Velocity is found from v = Cd x sqrt(2gh), and volumetric flow is converted from cubic feet per second to gallons per minute.
Worked Examples
Example 1: Residential Water Flow
Problem:A home has 60 PSI water pressure with a 0.5-inch supply line. What is the maximum flow rate?
Solution:Head = 60 x 2.31 = 138.6 ft\nArea = PI x (0.25)^2 = 0.1963 sq in = 0.001364 sq ft\nVelocity = 0.61 x sqrt(2 x 32.174 x 138.6) = 57.57 ft/s\nFlow = 0.001364 x 57.57 = 0.0785 cfs\nGPM = 0.0785 x 448.831 = 35.24 GPM
Result:Approximately 35.24 GPM at 60 PSI through a 0.5-inch orifice
Example 2: Fire Sprinkler Calculation
Problem:A sprinkler head operates at 25 PSI with a 0.375-inch orifice and Cd of 0.75.
Solution:Head = 25 x 2.31 = 57.75 ft\nArea = PI x (0.1875)^2 = 0.1104 sq in = 0.000767 sq ft\nVelocity = 0.75 x sqrt(2 x 32.174 x 57.75) = 45.73 ft/s\nFlow = 0.000767 x 45.73 = 0.03507 cfs\nGPM = 0.03507 x 448.831 = 15.74 GPM
Result:Approximately 15.74 GPM at 25 PSI through the sprinkler head
Frequently Asked Questions
How do you convert PSI to GPM?
PSI (pounds per square inch) measures pressure while GPM (gallons per minute) measures flow rate, so a direct conversion requires knowing the pipe or orifice diameter and a discharge coefficient. The method first converts PSI to a pressure head in feet using the factor 2.31 feet per PSI, then applies the orifice flow equation Q = Cd * A * sqrt(2gh) to get volumetric flow. Finally, the result is converted from cubic feet per second to gallons per minute using the factor 448.831.
What is the relationship between PSI and water pressure head?
Water pressure head expresses pressure as the height of a column of water that would produce that pressure. One PSI equals approximately 2.31 feet of water head, or equivalently, a column of water 2.31 feet tall exerts a pressure of 1 PSI at its base. This conversion is derived from the density of water (62.4 lb/ft3) and is fundamental in hydraulic engineering for calculating pump requirements, flow through pipes, and sprinkler system design.
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy