# Valve Flow Coefficient Cv / Kv

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Valve flow coefficient, abbreviared as $$C_v$$, also called valve sizing coefficient, a dimensionless number, is the number of US gallons of water at 60°F that will flow throuhg a valve in one minute when the pressure differential across the valve is one pound per square inch (psi).

## Valve Flow Coefficient Cv / Kv Formulas

 $$\large{ C_v = Q \sqrt{ \frac{SG}{\Delta P} } }$$ $$\large{ Q = C_v \sqrt{ \frac{\Delta P}{SG} } }$$ $$\large{ \Delta P = SG \left( \frac{Q}{C_v} \right) }$$ $$\large{ K_v = Q \sqrt{ \frac{SG}{\Delta P} } }$$ $$\large{ Q = K_v \sqrt{ \frac{\Delta P}{SG} } }$$ $$\large{ \Delta P = SG \left( \frac{Q}{K_v} \right) }$$

### Where:

 Units English Metric $$\large{ C_v }$$ = valve flow coefficient (US units) $$\large{ dimensionless }$$ $$\large{ K_v }$$ = valve flow coefficient (SI units) $$\large{ dimensionless }$$ $$\large{ Q }$$ = valve flow rate $$\large{\frac{ft^3}{sec}}$$ $$\large{\frac{m^3}{s}}$$ $$\large{ \Delta P }$$ = valve pressure differential $$\large{\frac{lbf}{in^2}}$$ $$\large{\frac{N}{m^2}}$$ $$\large{ SG }$$ = specific gravity of fluid $$\large{ dimensionless }$$