I am trying to determine the The information I have is:*valve CV*fluid *flowrate I want through the valve *an approximate downstream pressure. Is there any way I can calculate the upstream pressure or the pressure drop across the valve from this information? I have sent all this to the valve manufacturer for them to run through their program but was wondering if a manual calculation is do-able.inlet pressure to a throttle valve. Yes. Use the Cv equation appropriate for your application, and solve for P1. Post all the parameters you have and I will run it thru a sizing program. If the fluid is not commonly used, you might want to throw in the specific gravity. I did try using a Cv equation but was getting daft results. However, as I said in my original post, I sent the data to the valve manufacturer and they have now responded with a result from their software. Thanks for your response anyway.