In this paper, a new method is presented that allows the determination of partly unknown fuel properties. On the basis of process data that was measured online (mass flows, flue gas composition and temperature values), mass, elemental balances and statistic correlations, it is possible to determine the carbon, hydrogen, oxygen and water content, as well as the heating value of the supplied feedstock. The method further allows calculating the content of cellulose, hemicellulose, lignin and extractives, as well as the nitrogen and sulphur content by using additional knowledge of the chemical biomass composition and statistical relationships between the main components. The validation of the method is carried out with results of biomass combustion tests in a 300 kW(th) circulating fluidized bed combustion facility. It is shown that the fuel properties of three types of biomasses, which were determined by the new method, are in good agreement with the fuel properties determined by standardized fuel analysis methods. (C) 2017 Elsevier Ltd. All rights reserved.