The solid state density of an energetic material is one of the most important parameters related to performance. A new group additivity data base has been determined to provide atom and functional group volumes for the calculation of solid stare densities. Volumes for 78 atoms/groups were determined for C, H, N, O and F-containing structures from 11557 crystal structure data. Sets of linear volumes, from observed unit cell volume per molecule data, and nonlinear volumes, from observed crystal densities, were determined. The average percent difference between the observed volumes/densities for a 485 structure data base that was not used in the initial parametrization is 2.04%.