A correlation for the constant pressure heat capacity (C-p) valid from 50 K to the fusion temperature for pure organic solids is presented. The predictive correlation includes seven universal coefficients. The variables are temperature and a parameter alpha, which possesses a value proportional to the number of atoms in a molecule divided by molar mass. This parameter is shown to be more robust than molecular structure or composition as a descriptor for C-p. The training set comprises 72 organic solids with a wide range of molecular structures and elemental compositions including nitrogen-, oxygen-, and sulfur-substituted organic compounds. Solid-solid transition regions were excluded from the data set. The average absolute deviation for the comparison test set including 93 additional compounds with 2080 specific heat capacity values is less than 0.06 J center dot K-1 center dot g(-1). The principal applications for the correlation are estimation of heat capacities for large organic molecules, where data are normally unavailable, and for poorly defined mixed organic solids such as asphaltenes where elemental analysis but not molecular structures are available.