This paper introduces two novel simple correlations to assess crystal density of ionic molecular energetic materials as a new class of hazardous high energy density materials. The first one is based on only elemental composition, which can be corrected in the second correlation by two correcting functions on the basis of some molecular fragments in order to include intermolecular interactions. For 100 ionic CHNO molecular systems as training set, the root mean square (rms) percent deviations of predictions for these models relative to experiment are 5.4% and 3.2%, respectively. Corresponding average absolute errors for the new correlations are also 0.077 and 0.042 g/cm(3), respectively. These models have been validated with further the 48 ionic compounds as test set, where the computed results of two complex quantum mechanical models have been reported, which give good results. Moreover, the second revised correlation provides the lowest rms percent deviation and average absolute error of predictions for the tested ionic compounds relative to experiment, i.e., 2.3% and 0.036 g/cm(3), respectively. (C) 2015 Elsevier B.V. All rights reserved.