# Head Friction Loss in Fittings and Valves

This formula calculates the loss of head in a valve or fitting.

### Head Friction Loss in Fittings and Valves Formula

\(\large{ h_f = K \frac { v_{a}{^2} } { 2g } }\)

Where:

\(\large{ h_f }\) = head frictional resistance

\(\large{ v_a }\) = average velocity in the pipe

\(\large{ g }\) = gravitational acceleration

\(\large{ K }\) = resistance coefficient for fittings or valves

### Resistance Coefficient Formula

\(\large{ K = f \frac{l}{d} }\)

Where:

\(\large{ K }\) = resistance coefficient

\(\large{ l }\) = equivalent length

\(\large{ f }\) = friction factor

\(\large{ d }\) = inside diameter (ID)

Tags: Equations for Friction Equations for Valves Equations for Head Equations for Fittings