Abstract Generally, Bond work index is a common method for selecting comminution equipment as well as estimation of grinding efficiency and calculating required power. In the current research, a simple, fast and accurate procedure is introduced to find the rod-mill work index based on the conventional Bond work index. The grinding experiments were carried out on four typical samples of iron, copper, manganese and lead–zinc ore with three test-sieves in specified time periods and aimed to shortening the procedure. Furthermore, the grinding kinetics and mass balance equations were applied to model the standard Bond rod-mill work index. For comparing the standard Bond rod-mill work index and the new modeled method, work index ( W i ) and produced fine particles in a cycle ( G i ) for the four samples determined. The performed paired Student’s t -test results indicated that the Standard Deviation for G i and W i obtained by the shortened method are respectively 0.50 and 0.58 in respect of traditional Bond method.