The packing of solid particles is an important research topic in particle mechanics and powder technology. However, the packing density of particles is difficult to measure and predict. Although test methods for measurement and theoretical models for prediction have been developed, the measured results and predicted values do not always agree with each other. It is postulated herein that the discrepancies between the measured results and predicted values are mainly due to the wedging effect caused by fine particles trapped at narrow gaps between coarse particles, which has not been considered in the existing packing models. Such wedging effect is explained in the light of experimental results obtained by others and additional results obtained from a comprehensive experimental study conducted herein. It is incorporated into a new 3-parameter packing model, which provides a better insight into the packing structure of solid particles and is generally more accurate than the existing models. (C) 2013 Elsevier B.V. All rights reserved.