# Flow Coefficient

Flow coefficient, abbreviated as \(C_v\), can be described as the volume (in US gallons) of water at 60°F that will flow per minute through a valve with a pressure drop of 1 psi across the valve. This gives us a method to compare flow capabilities of different valves. The flow coefficient allows us to determine what size valve is required for a given application.

Flow Coefficient is primarily used when sizing control valves. However, it can be used to characterize other types of valves such as ball valves and butterfly valves.

## Formulas that use Flow Coefficient

\(\large{ C_v = Q \; \sqrt {\frac{SG}{\Delta p} } }\) | |

\(\large{ C_v = Q \; \left( {\frac{SG}{\Delta p} } \right) ^{\frac{1}{2} } }\) | (by volume) |

\(\large{ C_v = \frac {W}{500 \; \left( SG \; \Delta p \right) ^{\frac{1}{2}} } }\) | (by weight) |

### Where:

\(\large{ C_v }\) = flow coefficient

\(\large{ Q }\) = flow rate capacity

\(\large{ W }\) = flow weight

\(\large{ \Delta p }\) = pressure differential

\(\large{ SG }\) = specific gravity of fluid (water at 60°F = 1.0000)

Tags: Equations for Coefficient Equations for Pipe Sizing Equations for Flow Equations for Valve Sizing