# Resistance coefficient K and equivalent length l/d calculation for valves and fittings

Related calculators: Pressure drop; Pipe diameter; Airo flow

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Calculator can be used for resistance coefficient (or resistance factor) K and equivalent length l/d calculation for valves and fittings. Resistance coefficient K and equivalent length l/d is proportional coefficient between pressure drop (head loss) and square velocity of fluid flowing through valves and fittings like elbow, bend, reducer, tee, pipe entrance and exit, as follows:

where is:

• K - resistance coefficient
• v - velocity
• gn - acceleration of gravity

Relation between resistance coefficient and equivalent length is:

where is:

• K - resistance coefficient
• f - friction factor
• L - equivalent length
• D - internal diameter

The head loss due to resistance in valves and fittings are always associated with the diameter on which velocity occurs.

Resistance coefficient and equivalent length l/d calculator should be used with pressure drop calculator or with gas compressible flow calculator to calculate pressure drop in piping system that includes obstructions like fittings and valves.

Based on the size and shape of valves and fittings different values for resistance coefficient and equivalent length l/d are calculated. Calculator can be used for elbows, pipe bends, mitre bends, return bends, standard tee, pipe entrance, pipe exit and for sudden and gradual enlargement or contraction of pipe.