Estimate dynamic pressure from flow rate and inside diameter, or solve for GPH or diameter, with GPM, LPH, PSI, bar, kPa, and fluid-specific-gravity options.

Velocity-pressure estimate for an incompressible fluid. Pump discharge pressure, friction losses and elevation require other system data. Density = specific gravity ร—1,000 kg/mยณ.

Use the inside opening, rather than nominal pipe size.

Fluid density

1 represents the reference density of1,000 kg/mยณ. Adjust for the fluid and temperature.

GPH to PSI Formula

Flow alone cannot determine static pressure. This estimates dynamic (velocity) pressure from a circular inside diameter and density using q = ยฝฯvยฒ, with v = flow รท area. For US gallons per hour, square-inch area and density = SG ร— 1,000 kg/mยณ:

PSI = 1.9263598278 ร— 10โปโท ร— SG ร— GPHยฒ / Aยฒ

Variables:

  • PSI is estimated dynamic pressure in pounds per square inch; SG is fluid density divided by 1,000 kg/mยณ.
  • GPH is the flow rate in gallons per hour
  • Area is the cross-sectional area of the pipe in square inches

Convert flow and actual inside area to compatible units, divide flow by area for average velocity, then apply q = ยฝฯvยฒ. Dynamic pressure is a velocity term; it does not establish static pump discharge pressure or friction loss. See NASAโ€™s explanation of static and dynamic pressure.

GPH to PSI Conversion Table (Velocity pressure: density = 1,000 kg/mยณ, inside diameter = 0.5 in)
Gallons per Hour (GPH) Pounds per Square Inch (PSI)
100.000
250.003
500.012
750.028
1000.050
1500.112
2000.200
2500.312
3000.450
4000.799
5001.249
6001.799
7502.811
1,0004.997
1,2507.807
1,50011.242
2,00019.987
2,50031.229
3,00044.970
4,00079.946
* Rounded to 3 decimals. Formula used: PSI = 1.9263598278e-7 ร— (GPHยฒ) / Aยฒ, with A in square inches and specific gravity = 1. Here A = 0.19635 inยฒ (d = 0.5 in). Example: 1,000 US GPH โ†’ 4.997 psi.

What is GPH to PSI Conversion?

This calculator relates flow, circular inside diameter and dynamic pressure under an incompressible mean-velocity model. Real system pressure also depends on pump curves, static head, pipe length and roughness, fittings and outlet conditions. Use those data for system design.

How to Calculate Pressure from Flow Rate?

The following steps outline how to calculate the pressure from the flow rate.

  1. First, determine the flow rate (GPH) in gallons per hour.
  2. Next, determine the cross-sectional area of the pipe (Area) in square inches.
  3. Use the formula provided to calculate the pressure (PSI).
  4. Finally, use the calculator above to verify your result.

Example Problem :

Use the following variables as an example problem to test your knowledge.

Flow rate (GPH) = 300 gallons per hour

Pipe cross-sectional area (Area) = 2 square inches