# Graphic Standard Deviation

## Description

Is an approximate measure of sorting or variation of a particle size distribution in phi scale; can be estimated from the percentages of the particles which correspond to the percentages 84% and 16%

Related formulas## Variables

σ_{g} | Graphic Standard Deviation (ϕ) |

ϕ84 | Particle's percentage which corresponds to 84% phi unit (ϕ) |

ϕ16 | Particle's percentage which corresponds to 16% phi unit (ϕ) |

## Categories

### External links