The heat contents of various solid wastes materials (usually expressed as: British Thermal Units per pound or Btu/no. of sample) are important to establish an energy balance about an incinerator and thereby determine the efficiency of that incinerator. Also this heat value, especially of raw refuse, is considered when planning the design of an incinerator. The heat contents of incinerator residue and compost used for landfill are essential data for determining the stability of these waste products. The experimental method, of determining heat contents of prepared solid waste samples is sometimes difficult to perform and the accuracy of the data is, at times, questionable. The heat contents of such samples may be determined mathematically by a modified Dulong formula with data from ultimate analysis. This mathematical approach can either eliminate the need for experimental test or verify the accuracy of such test. Total heat of combustion content of a solid waste sample is defined as the oxidation of organic carbon to carbon dioxide, hydrogen to water, nitrogen to nitrogen dioxide, sulfur to sulfur dioxide, and the decomposition of carbonates present in the sample.