The topic of this diploma thesis is the calculation of a reinforced concrete building in an seismic load case. The default building is 21.75 [m] long,, 16.75 [m] wide, 16.8 [m] high. The entire structure is made of reinforced concrete. The diploma thesis includes the formation of a model in the SCIA program. In the model, the seismic load is given, so in this thesis only the seismic load case is considered. Modal and spectral analysis is performed on the model. After the modal analysis, an analysis of the load-bearing system for horizontal loads was performed according to HRN EN 1998, which determines the behavior factor of the structure. By carrying out spectral analysis, results were obtained based on which the dimensioning of the building wall is carried out. In addition to the building model, the thesis also contains the slab model, from which the results for the dimensioning of the slab were obtained. A static analysis, calculation and dimensioning of the staircase was carried out. Reinforcement drawings are attached for all previously mentioned elements.