# Differential Pressure Flow Rate Formula **URL:** \ **Category:** Ignition\ **Created:** [May 22, 2020, 2:31pm UTC](https://forum.inductiveautomation.com/t/differential-pressure-flow-rate-formula/34973 "2020-05-22T14:31:46Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![dcamp1](https://avatars.discourse-cdn.com/v4/letter/d/dc4da7/32.png) [@dcamp1](https://forum.inductiveautomation.com/u/dcamp1)\ **Post date:** [May 22, 2020, 2:31pm UTC](https://forum.inductiveautomation.com/t/differential-pressure-flow-rate-formula/34973/1 "2020-05-22T14:31:46Z")
I’m just asking to see if anybody can maybe point me to someone who I could ask questions about how to calculate flow rate of a GAS with differential pressure. These are the only variables that I have to work with. High Pressure (P1) in Psi Low Pressure (P2) in Psi Temperature Orifice Dia. Pipe Dia. Specific Gravity. Thanks for any help. ---
**Author:** ![bmusson](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bmusson/32/87530_2.png) [@bmusson](https://forum.inductiveautomation.com/u/bmusson)\ **Post date:** [May 22, 2020, 3:04pm UTC](https://forum.inductiveautomation.com/t/differential-pressure-flow-rate-formula/34973/2 "2020-05-22T15:04:19Z")
You’re looking for Bernoulli’s principle, with either assumptions made about the compressibility of your flow (isobaric/isochoric conditions), or use a suitable equation of state to solve for compressibility ([Redlich-Kwong](https://en.wikipedia.org/wiki/Redlich%E2%80%93Kwong_equation_of_state), Peng-Robinson, etc.). It’d probably be more cost effective to just buy a proper flow computer than to take the time to try and implement this yourself. [https://www.yokogawa.com/us/solutions/products-platforms/field-instruments/flow-meters/dp-flow/differential-pressure-flow-tertiary-elements/415-steam-and-gas/](https://www.yokogawa.com/us/solutions/products-platforms/field-instruments/flow-meters/dp-flow/differential-pressure-flow-tertiary-elements/415-steam-and-gas/) ---
**Author:** ![dcamp1](https://avatars.discourse-cdn.com/v4/letter/d/dc4da7/32.png) [@dcamp1](https://forum.inductiveautomation.com/u/dcamp1)\ **Post date:** [May 22, 2020, 8:18pm UTC](https://forum.inductiveautomation.com/t/differential-pressure-flow-rate-formula/34973/3 "2020-05-22T20:18:11Z")
Thanks for the reply, but that’s not an option. I’m taking over another project and I just need to be able calculate the flow rate with the variables I mentioned. ---
**Author:** ![diat150](https://avatars.discourse-cdn.com/v4/letter/d/a587f6/32.png) [@diat150](https://forum.inductiveautomation.com/u/diat150)\ **Post date:** [May 22, 2020, 8:26pm UTC](https://forum.inductiveautomation.com/t/differential-pressure-flow-rate-formula/34973/4 "2020-05-22T20:26:56Z")
I 2nd the previous poster, buy the right tool for the job. If you are dead set against using one then you need to research the aga3 flow calculation equation at a minimum, and you will need more info than you provided. ---
**Author:** ![bmusson](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bmusson/32/87530_2.png) [@bmusson](https://forum.inductiveautomation.com/u/bmusson)\ **Post date:** [May 22, 2020, 8:57pm UTC](https://forum.inductiveautomation.com/t/differential-pressure-flow-rate-formula/34973/5 "2020-05-22T20:57:08Z")
This type of calculation, which is trivial for liquids, is a _whole different ballgame_ for compressible flow. I’ve never heard of these folks, but they’re offing a gas flow library in Python which you could possibly integrate into Ignition. > **[AGA Gas Flow Libraries with Full Source Code - SCADACore](https://www.scadacore.com/tools/software-libraries/aga-gas-flow-library/)** > > American Gas Association (AGA) calculation source code in C++, Python, and C# to calculate gas flow. Our library includes code for AGA3, AGA7, AGA8, AGA11. DLL with Excel integration. Unless you’ve got a masters degree in fluids/thermodynamics you’re not going to be able to roll your own gas flow calculations with any degree of accuracy. ---
**Author:** ![dcamp1](https://avatars.discourse-cdn.com/v4/letter/d/dc4da7/32.png) [@dcamp1](https://forum.inductiveautomation.com/u/dcamp1)\ **Post date:** [May 23, 2020, 1:11am UTC](https://forum.inductiveautomation.com/t/differential-pressure-flow-rate-formula/34973/6 "2020-05-23T01:11:54Z")
Thanks again, I will dive deeper into this matter! I do appreciate the feedback.