Colebrook-White Formula
1/sqrt(f) = 1.14 – 2 log10 [e/D + 9.35/(Re x sqrt(f))]
f = friction factor
e = internal roughness of pipe
D = internal diameter of pipe
Re = Reynolds number
Friction factors for turbulent flow calculated by Pipe Flow Wizard are based on the Colebrook-White formula.
The friction factor for Laminar flow is calculated from f = 64/Re