# Moody diagram (friction factor)

Section summary
1. Introduction
2. Diagram

## 1. How to find the friction factor graphically ? The Moody diagram

The friction factor is used to calculate the pressure drop due to the flow of a fluid in a pipe. It represents the interaction in between the fluid and the pipe. There are different ways to calculate it, one can be graphical, using a Moody graph.

Note that the friction factor used here is Darcy (also called Darcy-Wesibach or Moody) friction factor.

## 2. Moody Diagram

The Moody diagram helps to answer very quickly to the following question : what is the friction factor in pipes ?

This diagram has been generated using Churchill correlation.

If one wants to calculate the Fanning friction factor, the results of this graph must be divided by 4.

How to calculate the relative roughness ? The relative roughness is calculated by dividing the pipe roughness ε over the pipe diameter D

Pipe roughness = ε / D

Source file
- Image
- Excel sheet