Calculating specific discharge and breakage rates is an essential part of developing a grinding model for dry ball milling. With this purpose, detailed sampling surveys were performed to collect size distribution data at the steady state conditions of the cement grinding circuits at different plants. Effects of operational and design parameters on specific discharge and breakage rate of particles in geometrically different multi-compartment ball mills were evaluated. Results indicated that, effects of mill throughput rate, compartment length and mill feed size distribution on discharge rate function and effects of mill diameter and ball size distribution parameters on breakage rate function could be reflected using the industrial scale data directly. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.