Since the processes of sedimentation, as well as the flow through solid and fluidized beds are governed by the same laws, different approaches are compared in order to find a single approximation function valid for all three processes. The equation published by Stichlmair for the drag coefficient of the fluid flow through solid and fluidized beds is suitable as a generally valid function, and leads to explicit solutions of the quantities sought after if Martin’s approximation of the drag coefficient determined by the flow of the fluid around a particle is used. The discussion of the function of particle flux rate of uniformly sized spheres R = f(C(v), u(t)), which is essential for the design of clarifiers, demonstrates that the counter-current created by settling spheres during sedimentation must not be neglected. If this effect is taken into account using a counter-current factor K(CC), the sedimentation process can be calculated for the homogeneous distribution of the solid particle concentration with the concentration factor K(Cv) which can be derived from Stichlmair’s relation.