---
title: "Colebrook-White Formula"
canonical: "https://help.innovyze.com/space/infodrainage2021v1/16547933/Colebrook-White%20Formula"
format: markdown
---
The Colebrook-White Formula is used for Velocity calculations within the software

![image](media://20ce5cbd-a034-42ae-a48b-32d7fd530fdf)

where:

V = Velocity, (m/s)

g = Gravitational acceleration

S = Hydraulic gradient (m/m)

v = Kinematic viscosity of fluid (m²/s)

k<sub>s</sub> = Effective roughness

D = 4 * Hydraulic Radius (m)


Typical k<sub>s</sub> values for storm drainage are 0.6 mm and 1.5 mm for foul sewage pipes.

> ℹ️ **Note**
> ℹ️ 
> ℹ️ InfoDrainage uses a fixed viscosity value of 1 centistoke = 1E-06 m²/s