Mode / Modal Particle Size

Modal particle size is the value in a particle size distribution that occurs most frequently – it represents the peak of the frequency distribution and is also referred to as the mode. While the mean particle size (D₅₀) divides the distribution into two halves, the modal particle size indicates the peak and can be significantly smaller or larger than the median, depending on whether the distribution is left- or right-skewed. Many technical powders show multiple peaks (multimodal distribution), for example when fine and coarse particles are mixed or agglomerates are present. In such cases, multiple modal particle sizes may be reported.
Knowing the modal particle size is important for optimizing filtration and classification processes. It indicates which particle size makes up the largest portion of the mass or number of particles. By selecting a pore size that retains the modal particle size, the majority of particles can be effectively separated. At the same time, larger and smaller fractions must be considered to achieve the desired filtrate quality.
Unlike the median, the mode is more sensitive to changes in the distribution, such as those caused by agglomeration or grinding. In ball milling, the modal value can be deliberately shifted by adjusting milling parameters. In granulation or fluidized bed processes, the modal particle size can be increased to improve dust control.
To determine the modal particle size, histograms are often created that show the frequency of measured particle size classes. Laser diffraction systems typically provide this data. Optical methods such as dynamic image analysis are also suitable for identifying peaks in the distribution.
Our consulting services include interpreting particle size distributions and selecting the appropriate filter fabric. In bimodal or multimodal distributions, it may be useful to use multi-stage filters or stepped pore structures to retain both modal and marginal fractions. By designing fabrics with application-specific variable mesh sizes, we can optimize the separation mechanism.