This paper presents a numerical method for calculating the maximum force a steel automobile door panel can support at its upper character line without creasing failures. The method is based on the concept of plastic work, that is, the non-recoverable energy dissipated in the panel by the applied force and plastic deformation. By relating the calculated plastic works and the measured creasing forces of twelve experimental panels, a threshold value of plastic work of 0.03 joule has been obtained for signaling the onset of creasing. This critical value was used to calculate the creasing forces of these panels. The results so obtained are accurate. They have an average error of less than six percent from their corresponding measured data. The correlation coefficient between the calculated and measured creasing forces is 0.97.