In this paper, a comprehensive methodology for calculating load sharing in multiple tooth contact is presented based on the experimental stress‐optical method of caustics. The technique is applied to a set of poly‐methyl‐methacrylate gears at various meshing positions covering a complete meshing cycle, including single and multiple gear tooth contact. The load sharing factor (LSF) is calculated using well‐established mathematical formulae from the photographs of the transmitted caustics and the obtained results are compared with the pertinent International Organisation for Standardisation and American Gear Manufacturers Association standards with which good agreement is verified. The proposed method is a reliable alternative for measuring load distribution in gear teeth compared with photoelasticity and other experimental techniques.