Calculate Valve Cv, or control valve size factor, is a term used in the business of engineering to measure the efficiency of valves. It is the ratio of the flow rate at an average pressure drop across the valve compared to the maximum potential flow when it is open fully and there is no pressure difference. No matter what type of application you are using, it is important to understand this term when working with valves. By accurately calculating this value, you can ensure that your operations will run as efficiently as possible – making sure that you get the most out of your equipment.