# Resistance Coefficient

Resistance coefficient, abbreviated as K, is a dimensionless number that 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)