In energy transformation processes, such as combustion of fossil and renewable fuels, the conservation of energy (first law of thermodynamics) as well as the quality of energy (second law of thermodynamics) is important. The objective of this article is to present a calculation of standard chemical exergy of coal-based fuels. In this regard, the necessity of this study has been based on solid and valid arguments on the advantages of second-law analyses compared to first-law analyses and a correct chemical exergy calculation is presented. A formula has been developed for estimating the chemical exergy of coals from their ultimate analysis values. In order to obtain this formula, 33 samples from different geographical regions in Turkey were analyzed to calculate chemical exergy values by using ultimate analyses and calorific values. Also, chemical exergy values of these coal samples obtained from different Turkish sources were calculated from a formula in the literature. The mean differences between these values range from 0.798 to 0.646%. The formula developed for estimating the chemical exergy of coals from their ultimate analyses and calorific values had a correlation coefficient (R-2 = 0.99), and the prediction of this formula is good, as well as expected.