PSI to GPM Calculator

Convert pressure and pipe size into water flow, or work backward from flow rate to PSI using the same Bernoulli-based page. This page also keeps the formula, examples, FAQs, and references close by so you can check the result with confidence.

What This PSI to GPM Calculator Helps You Do

For a 2.5-inch pipe and 72 psi tank pressure, the flow is about 1411 GPM. Review the formula and examples below if you want to see how the result is derived.

This page is meant to give you a fast answer, but it also helps you double-check the math before you make a decision. Start with the inputs that you already know, run the calculation, and then compare the output with the formula, examples, and FAQs below so you can see whether the answer fits the situation you are modeling.

If the result looks off, the usual causes are a unit mismatch, a missing decimal, the wrong scenario, or a value that needs to be entered as a rate instead of a total. The notes on this page are designed to make those checks easy without forcing you to leave the calculator and search for context elsewhere.

  • Use the calculator first for a quick estimate.
  • Use the formula to understand how the result is built.
  • Use the examples to compare common use cases.
  • Use the references when the answer depends on a standard or assumption.

Common Checks

A quick result is useful, but the best result is one that still makes sense when you look at it a second time. If you are comparing scenarios, try changing one input at a time so you can see which variable has the biggest impact on the final answer. That makes it much easier to spot whether the calculation matches your expectations.

It also helps to keep the context of the problem in mind. A calculator can tell you the math, but you still need to decide whether the input represents a total, a rate, an average, or a category-specific assumption. When in doubt, start with a simple example from the page and scale up from there.

  • Check that every unit matches the rest of the problem.
  • Keep rates, totals, and averages separate.
  • Adjust one variable at a time when testing scenarios.
  • Use the smallest realistic input first, then scale upward.

Scenario Planning

This calculator is especially useful when you want a quick answer before you commit time, money, or effort. Try one baseline input set, then change a single number and compare the result so you can see how sensitive the answer is to that variable.

That makes the page useful for more than just arithmetic. It becomes a small decision aid that helps you compare options, test assumptions, and explain the final number with confidence when you need to share it with someone else.

psi
psi
in
ft²
GPM/GPH

Converted Flow or Pressure

--

Quick Answer: For a 2.5-inch pipe and 72 psi tank pressure, the flow is about 1411 GPM. Review the formula and examples below if you want to see how the result is derived.

How to Calculate PSI to GPM Calculator

  1. Enter the pressure: Type the tank pressure and the exit pressure.
  2. Enter the pipe size: Use the pipe diameter or the cross-sectional area.
  3. Choose the flow unit: Pick GPM or GPH depending on how you want the answer shown.

PSI to GPM Calculator Formula

v = sqrt((ΔP × 144 × 32.174 × 2) / 62.4), Q = A × v
Variable Meaning Unit
ΔP Pressure difference psi
A Cross-sectional area ft²
Q Flow rate GPM or GPH

Worked Examples

USA - PSI to GPM
  • Pressure inside tank: 72.0 psi
  • Pressure at the exit: 14.7 psi
  • Diameter of the pipe: 2.5 in

Result: 1411.6 GPM

Matches the Omni example closely.

UK - GPM to PSI
  • Flow rate: 1411.3 GPM
  • Pressure at the exit: 14.7 psi
  • Diameter of the pipe: 2.5 in

Result: 72.0 psi

Reverse calculation using the same pipe.

EU - Using pipe area
  • Pressure inside tank: 72.0 psi
  • Pressure at the exit: 14.7 psi
  • Cross-sectional area: 0.03409 ft²

Result: 1411.6 GPM

Area mode gives the same result as diameter mode.

PSI to GPM reference

Example values from the Bernoulli-based conversion.

Range Meaning Action
< 100 GPM Low flow Check whether the pipe diameter should be larger.
100-1000 GPM Moderate flow Use the result directly and keep the same flow unit.
> 1000 GPM High flow Verify the pressure assumptions and pipe size carefully.
Example values from the Bernoulli-based conversion.
Tank PSI Exit PSI Pipe diameter Approx. flow
72.0 14.7 2.5 in 1411 GPM
50.0 14.7 2.5 in 1141 GPM
72.0 14.7 3.0 in 2026 GPM
72.0 14.7 2.5 in 84,681 GPH

Frequently Asked Questions

Yes. Enter the tank pressure, exit pressure, and pipe diameter.

Yes. Switch the pipe input mode to area.

Yes. Choose PSI as the solve-for mode.

Yes. Choose GPH in the flow unit dropdown.

Yes. It is free to use online.
Planning note: This calculator uses a Bernoulli-based water-flow approximation.

References

Last reviewed: March 28, 2026