A comprehensive model for the index void ratios and of sands is presented. It is based on a large set of previously published sand properties as well as tests on 25 new materials including glass spheres and two types of rice. The new model uses the index void ratios of perfectly uniform spherical glass beads as baselines to which factors accounting for the three most influential intrinsic soil properties are applied. The three properties are particles roundness, , sphericity, , and the coefficient of uniformity, . The following three factors led to the new model’s improvement over previous such efforts: (1) use of sands spanning a wide range of , , and values; (2) consideration of the combined and coupled effects of , , and ; and (3) utilization of a recently developed computational geometry method on digital images to obtain precise values of and for large, statistically reliable numbers of particles.