The aim of this paper was to introduce the estimation of the losses in the prototypes of the microwave devices. We proposed in this paper two algorithms: an algorithm for evaluation of losses in the microwave devices based on a waveguide and an algorithm for evaluation of losses in the microwave devices based on a meander line. In order to verify the results of losses evaluation for the waveguide-based device, we have used the electrodynamic model of the open cylindrical gyrotropic waveguide with one anisotropic dielectric layer and the electrodynamic model of the open cylindrical gyrotropic waveguide with two dielectric layers. In order to verify the results of losses evaluation for the meander line-based device, we have used the model of the meander line with asymmetrical periodical inhomogeneity. The comparison of the losses evaluation results received by the algorithms proposed in this paper and the results received by application of the commercial software together with the alternative methods confirmed that the proposed algorithms produced correct results.