# Sauter mean diameter ( surface diameter)

## Description

Sauter mean diameter (SMD, d32 or D[3, 2]) is an average of particle size. It is defined as the diameter of a sphere that has the same volume/surface area ratio as a particle of interest. SMD is typically defined in terms of the surface diameter and volume diameter. SMD is especially important in calculations where the active surface area is important. Such areas include catalysis and applications in fuel combustion.

Related formulas## Variables

d_{s} | The surface diameter (mm) |

A_{p} | The surface area (mm^{2}) |

π | pi |