We developed a new approach to evaluation of the intensity of osteogenic differentiation of mesenchymal stromal stem cells based on measurement of optical density of mesenchymal stromal cell cultures in a concentration range 625-10,000 cells per well after their culturing in osteogenic induction medium and staining of calcium deposits by the method of von Kossa. The proposed method allows comparative semiquantitative evaluation of osteogenic properties of mesenchymal stem cells depending on tissue sources (bone marrow, adipose tissue, placenta), in vitro cell density, number of passages, duration of culturing, and concentration of serum growth factors in the microenvironment. The developed approach makes it possible to compare functional activity of mesenchymal stromal cells in various pathologies. The proposed method can be used in traumatology and orthopedics for improving the efficiency of transplantation of mesenchymal stromal cells for stimulation of reparative osteogenesis.