The design approaches are not rated for gear tooth volume, the designers are not aware of the loss or gain on the cost, and failure or success of the design. This study provides a novel method to rate and convert textbook gear design approaches into ANSI/AGMA standard. The steel pinions with lowest and highest strengths covering minimum and maximum strengths available for the gear design meshing with cast iron gear were used in order to ensure that the method presented is generic. The method relies on obtaining design data (module m (mm) and face width F (mm)) for the most common design approaches considering bending fatigue. The gear design approaches are rated for the loss or gain using dimensionless geometric rating numbers, and then dimensionless conversion factors are obtained. Mean values of conversion factors independent of input power for the desired speed ratio are used to derive correlation equations for converting the design results of the selected approach to ANSI/AGMA standard. The method verified by case studies is generic and applicable to any gear design approach. Now, the most commonly used spur gear design approaches are rated by considering the gear volume. Furthermore, m and F obtained from the easiest textbook design approaches can be easily converted into the most accurate but more complicated, challenging and time-consuming ANSI/AGMA standard with minimum effort and error. It does not only allow saving time and resources but also provides safer and reliable designs for designers who are not bound to use a specific gear standard.