Laser diffraction is a quick and reliable method used to determine the particle size distribution of materials ranging from submicron- to millimeter size (ISO 13320). Laser diffraction measures particle size distributions by measuring the angular variation in intensity of light scattered as a laser beam passes through sample dispersed in a suitable suspension fluid.

The angular scattering intensity data is analysed to calculate the size of the particles using the Mie theory if the optical properties of the material are known. A simplified approach is to use the Fraunhofer approximation, which does not require knowledge of the optical properties of the sample.

By this technique, many particles are analyzed to obtain a statistically significant particle size distribution. The particle size is reported as volume percentage equivalent spherical diameter.