What Cv means
The flow coefficient (Cv) is a standard measure of how much liquid a valve will pass for a given pressure drop — a higher Cv means the valve allows more flow for the same pressure drop, and it’s widely used for valve sizing and selection.
The formula
For liquid flow, Cv = Q × √(SG / ΔP), where Q is the flow rate in US gallons per minute, SG is the fluid’s specific gravity relative to water, and ΔP is the pressure drop across the valve in psi.
This is the standard imperial valve-sizing formula used in process and fluid power engineering references.
Last reviewed August 2026