The traditional Moody diagram is still much used for determining the Darcy-Weisback friction factor as a function of Reynolds number and relative surface roughness. As explained in Pipe Flow 1, Chapter 2, the traditional diagram is a bit outdated and no longer the most accurate alternative . The modified Moody diagram builds on measurements which were not available when the original diagram was created and is therefore better, particularly for very high and transitional Reynolds numbers (just click a diagram to enlarge).
