A method for estimating entropy of crystal phases at 298.15 K, when a direct calculation from heat capacity data is not possible due to a limited range of temperature for C-p measurements, is proposed. It was shown that a reasonable estimation of S-298.15 degrees for the substances with predominant lattice contribution can be achieved by approximation of heat capacities from "nitrogen" to room temperature by the combination of Einstein functions and by correction of the obtained entropy value with the scaling coefficient. The same result can be obtained in the presence of an additional contribution to the heat capacity, connected with the settling of upper energy levels if there are data for a priori estimation of the corresponding contribution.