# Fanning Friction Factor

Fanning friction factor, abbreviated as f, a dimensionless number, is the ratio of shear stress acting on the surface of a solid. Fanning friction factor is not the same as the Darcy friction factor. It is equal to 1/4 the Darcy friction factor. Since they are basically the same, you need to note which one is being used when doing calculations. This can be done by using the subscript F, f_{F}

## Formulas that use Fanning Friction Factor

\(\large{ f = \frac{ \tau }{ \rho \; \frac{Q^2}{2} } }\) | |

\(\large{ f = \frac{ 16 }{ Re } }\) |

### Where:

\(\large{ f }\) = Fanning friction factor

\(\large{ \rho }\) (Greek symbol rho) = density of fluid

\(\large{ Re }\) = Reynolds number

\(\large{ \tau }\) (Greek symbol tau) = shear stress

\(\large{ Q }\) = velocity of bulk flow