Hitherto the method of laser diffraction has been used only for determining particle size distribution (PSD) of mixtures. This paper presents an extension of that measurement approach to include the determination of the number of particles. The described method may find practical application in a variety of disciplines, including biology (e.g. for determination of population sizes of micro- and mesofauna), agricultural sciences (e.g. with relation to the study of soils), and Earth science (e.g. with relation to sediments and lands), among others.