The factors listed above are related in a contradictory way. For example, flowability increases with increasing particle size, but at the same particle size distribution it can be different due to different specific surface area. In almost all cases, the flowability of powders, as measured by funnel flow time, decreases with decreasing particle size due to an increase in the contact area. Spherical particles have better flowability than, for example, needle or lamellar particles. A decrease in bulk density reduces fluidity, but for the same bulk density substances will have different fluidity, as it depends on the shape of the particles and the coefficients of inter-particle friction. Most often, fluidity is determined by the rate of pouring a certain amount of material (30-100 g) from a metal or glass funnel with strictly specified geometric parameters and by the angle of natural slope.

This technological characteristic can be used in the selection of tabletting technology. Powdery mixtures containing 80-100 % of fine fraction (particle size less than 20 microns) are poorly dosed, therefore it is necessary to carry out directed particle enlargement of such mixtures, i.e. granulation. If the content of the fine fraction is up to 15 %, it is possible to use the method of direct pressing. Pressability is the ability of powder particles to cohesion under pressure, i.e. the ability of particles under the influence of electromagnetic forces (molecular, adsorption, electrical) and mechanical meshing to mutual attraction and adhesion with the formation of a stable strong pressing. In this case, the powder particles seem to fuse, stick together, adhere to each other to form a homogeneous solid.