While entrained-flow coal gasifiers (EFCGs) have been widely used in coal-gasification technologies, the thermal-calculation method, which is important for assessing the design and operation of EFCGs, has never been reported. Based on the fundamental thermal-calculation method for coal-fired boilers, and combined with the two-stage equilibrium model through the difference between the gasification and exit temperatures, we propose a thermal-calculation method for EFCGs to calculate the syngas composition, carbon conversion and energy distributions. The calculated gas compositions and heat loss are in good agreement with experimental data for industrial-scale plants. In the two-stage equilibrium module, the function for calculating the water participation ratio involved in the first-stage equilibrium reaction is improved by considering the influences of the ratios of oxygen/carbon and water/carbon, in addition to the gasification temperature. As the carbon conversion efficiency is significantly influenced by the oxygen/carbon and water/carbon ratios in the first-stage equilibrium system, the calculated carbon conversion efficiencies correspond more closely to the experimental data than the other models considering only the gasification temperature. (C) 2018 Published by Elsevier Ltd.