This paper presents the complete project of a modular multi-storey steel structure and all the details from its design to the calculation of the structure and its load analysis. The first part refers in general to all parking garages as a whole and it is shown what basic things they should consist of, the division of garages, their role and the future of garages in terms of automation. The second part mentions the material for making garages with a focus on steel, its advantages compared to concrete and the method of transporting and assembling the structure together with questions about the safety of the structure itself and its maintenance. The third part shows the design and dimensions of the garage itself, the location where it is located, and all types of used profiles, screws, retaining plates, and how they are connected to each other. This part also contains the economic aspect of building a three-story modular steel garage, that is, the estimated total cost of its entire construction from the ground up. The last part of the work refers to the calculation of all possible real loads to which the structure will be exposed, i.e. its limit state of usability with computer support and displays thereof.