Herein, a framework for the estimation of the thermodynamic properties of molecular crystals via the refinement of frequencies from density functional theory calculations against X-ray diffraction data is presented. The framework provides an efficient approach to including the contribution of acoustic modes in the thermodynamic properties. The obtained heat capacities for urea, the alpha- and beta-glycine polymorphs, benzoic acid, and 4 '-hydroxyacetophenone are in good agreement with those from adiabatic calorimetry.