Volumetric flow

..."To find the velocity of the fluid flow, multiply the differential pressure by two and divide this number by the density of the flowing material. As an example, assuming a differential pressure of 25 Pascals (or Pa, the unit of measurement of pressure) and the material is water, which has a density of 1 kilogram per meter cubed (kg/m^3), the resulting number will be 50 meters squared per seconds squared (m^2/s^2). Call this result A.

Find the square root of result A. Using our example, the square root of 50 m^2/s^2 is 7.07 m/s. This is the velocity of the fluid."...

https://sciencing.com/how-8233646-cross-sectional-area-pipe.html

...."The simplest equation for the flow rate Va is

Va = (ΔPD^4)/128μL

where ΔP is the pressure drop, D is the diameter of the pipe, μ is the viscosity and L is the length of the pipe.

If it’s air that is the fluid through the pipe, μ = 1.825x10^-5kg/m-s

Be careful with your units: Va will be in M^3/s"...

https://www.quora.com/Is-it-possible-to-calculate-the-flow-and-velocity-of-air-in-a-pipe-knowing-the-pressure-at-both-ends

d: Pipe Inner Diameter (in)

v: Air Velocity (ft/s)

Qa: Air Flow Rate (Actual) (CFM)

https://www.tlv.com/global/US/calculator/air-flow-rate-through-piping.html