We present an explicit representation of molar entropy for gaseous substances. Fortunately, through comparison of theoretical and experimental results, we discover that the molar entropies can be successfully predicted by applying experimental values of only four molecular constants for the carbon monoxide, hydrogen chloride, hydrogen fluoride, deuterium fluoride, gaseous boron monobromide, and nitrogen monoxide. The present entropy calculation scheme provides opportunities for predicting successfully entropy values of other gaseous substances with no use of a large number of experimental spectroscopy data. (C) 2017 Elsevier B.V. All rights reserved.