This paper presents an approach that has been developed to calculate the power draw of each size within a distribution of charge in a tumbling mill. Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to test the methodology. Experiments are conducted using dry spherical glass bead charge in a laboratory scale tumbling mill, which is mounted with a torque transducer and tachometer to provide measurements of mill power. Particle tracking information from PERT is used to reconstruct the motion of glass beads and infer the overall charge behaviour, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz-Mindlin contact model. For both sets of data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all cases investigated. (C) 2016 Elsevier B.V. All rights reserved.