A stirred milling model, based on the concept of shear-volume power, was developed and applied to geometries typically found in mineral processing systems. Generalising this model permits its use to model more complex mill geometries, such as those describing a tapered disk mill and the CoBal mill. Due to the additive property of the shear-volume power, the calculation of the power of complex mills is possible through geometric decomposition. This approach is supported by the calculation of the shear-volume power of a number of simple geometries commonly found in mills, and is used in the calculation of the shear-volume power of a tapered disk mill and the CoBal mill. Finally, by incorporating a breakage model, an equation that offers some usefulness in the design, operation and optimization of stirred mills is presented. (c) 2015 Elsevier Ltd. All rights reserved.