In this study, various approaches to and combinations of imperfections are investigated using geometrically and materially non-linear analysis with imperfections (GMNIA) of unstiffened buckling plates. These imperfections have a decisive influence on load-bearing behaviour during stability failure (plate buckling). When applying GMNIA, the user can opt for either equivalent geometric imperfections or a combination of geometrical and structural imperfections as given in EN 1993-1-5 Annex C. Here, the exact influence of the individual imperfections and their combinations on the load-bearing behaviour is not conclusively clarified. Furthermore, EN 1993-1-5 Annex C does not contain a recommendation for a suitable residual stress model. The aim of this investigation is to compare the ultimate load due to compressive stress using different approaches to imperfections. Six different combinations are analysed using GMNIA. The results make it clear that a variety of ultimate loads lie above the Winter curve for larger related slenderness values, 𝜆 ̅ 𝑝 , and thus lead to non-conservative ultimate loads. In addition, initial recommendations for the required size of the imperfection are given for the application of equivalent geometric imperfections depending upon the related slenderness, 𝜆 ̅ 𝑝 . Applying adjusted equivalent geometric imperfections to square plates under compressive stress achieves very good agreement with the Winter curve in the range relevant to the construction industry.