# Colebrook-White Equation

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Colebrook-White equation, also called Colebrook equation, is used toiteratively solve the Darcy-Weisback friction factor. This equation uses US units. To convert between US and SI units, use our calculator.

## Colebrook-White Equation formula

 $$\large{ \frac{1}{\sqrt{f}} = -2 \; log_{10} \left( \frac{ \epsilon\ }{ 3.7 \; d_h } + \frac{ 2.51 }{ Re \; \sqrt{ f } } \right) }$$

### Where:

 Units English Metric $$\large{ \epsilon }$$ (Greek symbol epsilon) = absolute roughness $$\large{ in }$$ $$\large{ mm }$$ $$\large{ f }$$ = friction factor $$\large{ dimensionless }$$ $$\large{ d_h }$$ = hydraulic diameter $$\large{ in }$$ $$\large{ mm }$$ $$\large{ Re }$$ = Reynolds number $$\large{ dimensionless }$$

Tags: Flow Equations