In response to recent earthquake events in Croatia, the pressing need for a swift and dependable approach to seismic assessment of existing masonry structures, such as [1] has surfaced. The proposed method is developed for rapid seismic assessment of existing masonry structures. Given the layout of load-bearing walls, with a few additional pieces of information, such as the number of storeys, slab and wall thicknesses, the method performs a real-time structural checks according to Eurocode geometric requirements [2]. Following that, a modal analysis is applied to unveil the dynamic behaviour of the structures, assisting users in formulating retrofit measures with an optimization objective for structural regularity. Buildings undergo analysis, considering parameters such as compactness, uniformity, symmetry, slenderness, and the percentage of walls in two directions. As a result, the proposed method enables efficient assessment of the buildings’ geometric characteristics and gives an overview to a designer if the existing masonry building is safe according to the adopted standards. Moreover, this tool provides professionals with an initial insight into the structural behaviour of the building, guiding decisions on whether to invest in destructive or non-destructive tests for a thorough seismic assessment of masonry structures. The proposed procedure has been tested and its reliability is validated by assessing 103 residential buildings affected by the 2020 Zagreb earthquake. This entire workflow is seamlessly integrated into a user-friendly digital tool implemented in Grasshopper and Rhino3D visual programming software. As part of future development, there is a plan to incorporate assessment of vulnerability and a optimization algorithm into the workflow. This algorithm aims to plan retrofit measures with considerations for cost-effectiveness, reliability, and minimal disruption to residents.