# Resistance Coefficient

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Resistance coefficient, abbreviated as K, a dimensionless number, represents how much resistance to flow the obstruction presents.  This is the inverse of flow coefficient which is how much flow capacity an obstruction allows.

### Resistance Coefficient Formula

$$\large{ K = f_d \; \frac {l} {d} }$$

Where:

$$\large{ K }$$ = resistance coefficient

$$\large{ f_d }$$ = Darcy friction factor

$$\large{ l }$$ = length of pipe

$$\large{ d }$$ = pipe inside diameter

$$\large{ \frac{l}{d} }$$ = equivalent length of the obstruction (dimensionless)