The Continuous Strength Method (CSM) is a new strain based design approach developed for nonlinear metallic materials, and has recently been successfully used for stocky stainless steel sections for which the benefit of strain hardening is more pronounced. Typically available stainless steel cross-sections are quite slender, and their failure is dominated by local plate buckling before yielding showing significant post buckling, which does not allow the definition of cross-section deformation capacity currently adopted in CSM. In this paper, a concept of equivalent elastic deformation capacity is introduced for slender sections, and the scope of CSM is extended to predict capacities for slender cross-sections under compression. Design guidelines are proposed to calculate equivalent elastic deformation capacities for various cross-section types using the current knowledge of CSM, which is used to predict the ultimate section capacity when subjected to compression. The proposed rules are verified against all available test results, and are found to in good agreement with experimental evidence.