PSI to GPM Calculator: Pressure to Water Flow Rate

PSI To GPM Calculator

PSI to GPM Calculator

Convert pressure to water flow rate

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PSI (pressure) alone can't tell you flow rate — you also need to know how restrictive the opening is. This calculator uses the standard valve/orifice flow equation: Q = Cv × √(ΔP / SG), where Cv is the flow coefficient of the valve, nozzle or orifice.

If you don't know Cv directly, switch to Orifice Mode to estimate it from the orifice diameter and a typical discharge coefficient.

Pressure Drop (ΔP)

PSI

Flow Coefficient (Cv)

Specific Gravity of Fluid

💧 Your Result

Flow Rate

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Enter values above to calculate

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GPM

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Liters/min

Calculation

PSI alone can’t tell you flow rate, you also need to know how restrictive the opening is, this calculator applies the standard valve/orifice flow equation to convert pressure drop into an actual flow rate in GPM.

How to use this PSI to GPM calculator

Choose your mode: Flow Coefficient (Cv), or Orifice Diameter.
Enter the Pressure Drop (ΔP) in PSI.
Enter the Flow Coefficient (Cv), or the Orifice Diameter if you don’t know Cv directly.
Enter the Specific Gravity of the fluid (1.0 for water).
Read the Flow Rate in GPM and Liters/min.

What this calculator does

This calculator uses the standard valve/orifice flow equation, Q = Cv × √(ΔP ÷ SG), where Cv is the flow coefficient of the valve, nozzle, or orifice, a manufacturer-specified value describing how much flow it passes for a given pressure drop.

Q (GPM) = Cv × √(ΔP ÷ SG)

Using Orifice Mode when you don’t know Cv

If you don’t know a component’s Cv directly, but do know its orifice diameter, Orifice Mode estimates the equivalent Cv from the orifice diameter and a typical discharge coefficient (Cd assumed at 0.61, typical for a sharp-edged orifice), letting you still get a usable flow estimate without a manufacturer’s flow coefficient spec sheet.

Why specific gravity matters for non-water fluids

The flow equation is calibrated so that water (specific gravity 1.0) is the baseline reference. Denser fluids flow more slowly through the same restriction at a given pressure drop, while less dense fluids flow faster, which is why entering the correct specific gravity for your actual fluid matters if you’re not working with plain water.

Frequently asked questions

What is a flow coefficient (Cv)?

Cv is a manufacturer-specified value describing how much fluid a valve, nozzle, or orifice will pass for a given pressure drop, it’s the key parameter in the standard flow equation used to convert PSI into an actual flow rate.

Can I estimate flow rate if I don’t know the Cv value?

Yes, switch to Orifice Mode and enter the orifice diameter instead, this calculator estimates an equivalent Cv using a typical discharge coefficient (0.61) for a sharp-edged orifice.

Why does the fluid’s specific gravity affect the flow rate?

The flow equation is calibrated with water (specific gravity 1.0) as the reference, denser fluids flow more slowly through the same restriction at a given pressure drop than water would, while less dense fluids flow faster, so entering the correct specific gravity is necessary for non-water fluids.