A mathematical modeling for stepped solar still performance is carried out which is not found in most of the previous studies. Computer programs (using Pascal language) are developed for achieving this mathematical model. Effect of the parameters of the still configuration such as the still width (b s ), depth of water (d w ), tray width (W) and the height of tray (H) on the still's performance. Comparisons between the obtained theoretical results and the experimental results from other researches are carried out to corroborate the proposed mathematical model. Comparing thermal performance of the stepped solar still with that of the conventional one shows that the stepped solar still is more efficient. The daily productivity of the conventional and stepped solar stills are found to be 4.0 and 4.51 (kg/m 2 day); separately. The daily efficiency of the conventional and stepped solar stills are 61.48% and 78.33%, individually.