In order to obtain correctly curvature radii and 90 degree wall angles after spring-back in roll bending process when making door panel products of automotive industry, finite element method (FEM) was first used to predict spring-back occurrence by changing various die radius and bending angles. Based on the relationship between the curvature radius/wall angle measurements after springback (output data) and die radiuslbending angle values (input data), a MATLAB tool is then used to express output data as functions of input data utilizing surface fitting method. Depending on the desired shaped of products the authors can easily calculate die radius and bending angle by solving system of nonlinear equations. Finally, obtained die radii and bending angles for random cases were simulated, measured and compared with desired ones. The simulation results were in good agreement with the calculations of die radius and bending angles.