A simple method for calculating the properties of combustion products is presented. The method is generic: the same equations apply to any fuel for any fuel-air ratio and temperature. The equations are suitable for both hand calculations and computer applications requiring repetitive property evaluations. The present equations offer accuracy comparable with the most elaborate method available but at a significantly reduced computational cost. The theory should find direct use in design-point and off-design performance calculations and optimization of internal combustion engines, e.g. gas turbine plants, calculation of the three-dimensional flowfield within a multistage turbine, and other applications requiring properties of combustion products..