A combined mathematical model for granule size distribution and cold bed permeability in the iron ore sintering process is presented. The combined model is obtained by integrating the models for granulation and cold bed permeability. The granulation model is based on the two-stage granule growth mechanism and incorporates exclusion principle along with layer thickness postulates of granulation. The permeability model consists of equations for velocity of gases through the bed and the cold bed voidage. The velocity of gases is predicted using a modified Ergun equation. The bed voidage is related to the spread of the granule size distribution as well as the possible deformation of granules during charging by incorporating moisture and fines content of raw sinter feed. The model simulation of granule size distributions, cold bed voidage and velocity of gases under different operating conditions compare well with experimental data from a laboratory sintering unit. Starting from the size distribution of raw feed and its moisture content, the model predicts the granule size distribution and the cold bed voidage and permeability, without introducing any intermediate measurements. Moreover, it can be integrated with a sintering model in order to describe the complete iron ore sintering process in a quantitative fashion.