The paper defines an updated method for “soil – reinforced concrete foundation” calculation that takes into account their mutual interaction. In this method, both the foundation structure and the footing structure are represented by a rigid-plastic model, which makes it possible to determine the bearing capacity of the system. This method eliminates the possibility of destruction of the reinforced concrete foundation from punching to the exhaustion of its bearing capacity. It further presents the results of the test conducted by the authors at Novocherkassk School for Soil Mechanics Research to validate the theoretical calculations attained with the use of the proposed method, as well as the results of tray testing of reinforced concrete foundation models. The calculation of the bearing capacity by the modernized method gives values close to the results of experimental studies. The authors discuss the challenge of determining the strength of sand base, which is known to affect the calculation of load-bearing capacity, and further propose a solution that uses piecewise linear limit line of shear strength of soil and has been developed in an attempt to increase the accuracy of calculations.