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Free PSI to GPM calculator for determining water flow rate in gallons per minute (GPM) from pressure difference (PSI) and pipe dimensions. Our calculator uses Bernoulli's equation for incompressible fluids to provide accurate flow rate calculations. Perfect for hydraulic systems, plumbing design, irrigation systems, and fluid dynamics applications.
Last updated: January 24, 2026
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Default: 14.7 psi (atmospheric pressure)
Enter either diameter or cross-sectional area
How it works:
Enter the pressure inside the tank and at the exit, then provide either the pipe diameter or cross-sectional area. The calculator uses Bernoulli's equation to determine the flow rate.
Definition
1 PSI = 1 lbf/in²
PSI measures pressure - the force applied per unit area. It's commonly used in the United States for measuring pressure in various applications.
Definition
Volume flow rate
GPM measures flow rate - how fast liquid moves through a pipe or system. It's essential for sizing pumps, pipes, and hydraulic components.
For a tank with 72 PSI pressure, 14.7 PSI exit pressure, and 2.5 inch pipe diameter:
Pressure Difference
57.3 PSI
Flow Rate
~1,412 GPM
Pipe Diameter
2.5 inches
Our PSI to GPM calculator uses Bernoulli's equation for incompressible fluids to determine flow rate from pressure difference and pipe dimensions. The calculation accounts for pressure differences, fluid density, and pipe cross-sectional area to provide accurate flow rate estimates for water systems.
P₁ + ½ρv₁² = P₂ + ½ρv₂²For horizontal flow: P₁ - P₂ = ½ρ(v₂² - v₁²)Velocity: v = √[2(P₁ - P₂) / ρ]Flow Rate: Q = v × AWhere P is pressure, ρ is fluid density, v is velocity, and A is cross-sectional area. For water at standard conditions, density is 62.4 lb/ft³. The calculator assumes the tank velocity (v₁) is negligible compared to the pipe velocity.
The calculator performs the following steps to convert PSI to GPM:
PSI to GPM calculations are essential in many engineering and practical applications. Hydraulic system designers need to know flow rates to size pumps and pipes correctly. Plumbers use these calculations to ensure adequate water pressure and flow. Irrigation engineers calculate flow rates to design efficient watering systems.
The calculator uses ideal fluid dynamics assumptions (Bernoulli's equation for frictionless, incompressible flow). In real-world applications, factors like pipe friction, fittings, valves, and fluid viscosity will reduce actual flow rates. The calculated values represent theoretical maximum flow rates under ideal conditions.
Need help with other conversions? Check out our pressure converter and volume conversion.
Get Custom Calculator for Your PlatformResult: Flow rate is approximately 1,412 gallons per minute (GPM)
This calculation assumes ideal conditions with no friction losses. Actual flow rates may be lower due to pipe friction, fittings, and other real-world factors.
30 PSI tank, 14.7 PSI exit, 1 inch pipe
Flow rate ≈ 113 GPM
50 PSI tank, 14.7 PSI exit, 4 inch pipe
Flow rate ≈ 1,808 GPM
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