Scale-up is a process of developing a larger version of a processing machine based on the performance of a smaller machine. For mills, scale-up is made difficult by the different rates at which different physical processes occurring within the machine change with the increasing size. Discrete Element Method (DEM) modelling can now be performed at a range of scales and can be used to help understand scale-up issues for mills. This paper explores the ways in which DEM can be used to assist in the scale-up process for a mill using the HICOM mill as a case study. By choosing speeds at each mill size that have the same charge distribution and structure a scale-up relationship is developed which allows prediction of the power draw with increasing mill size. Similar scale-up relationships are developed for the specific power intensity and the most common collision energy occurring within the charge. The peak loads on the liner and at the nutation point of the mill are key inputs to mechanical design. Their variation with increasing physical size is also explored. Finally, the change in wear behaviour with increasing scale is also determined. This scale-up process can be applied to any form of mill. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.