The three-roll bending process is a simple procedure, commonly used in the industry, through which a cylindrical surface can be produced from a sheet plate. This process is mainly controlled through experience and it is described with the finite element method, except for a very few numerical and analytical investigations. The topic of this article is to present a numerical method, through which the curvature function along the rolling direction can be calculated. This article presents the proposed numerical method and its verification with the finite element method. The results of the two numerical methods are in good agreement.