In this paper, a new approach is proposed for simplifying the calculation of flue gas specific heat and specific exergy value in one formulation depending on fuel chemical composition. Combustion products contain different gases such as CO2, SO2, N-2, O-2, H2O and etc., depending on the burning process. Specific heat and exergy of the flue gas differ depending on the chemical composition of fuels, excess air ratio and gas temperature. Through this new approach, specific heat and specific exergy value of combustion products can be estimated accurately in one formulation by entering the chemical composition of fuels, excess air ratio and gas temperature. The present approach can be applied to all carbon based fuels, especially biomass, fossil fuels and fuel mixtures for co-combustion and is so suitable for practical estimation of flue gas specific heat and specific exergy values provided that the fuel chemical composition is given. (C) 2009 Elsevier Ltd. All rights reserved.