The total temperature achieved by vitiation of air using hydrogen–oxygen combustion is predicted after heat transfer losses. The adiabatic temperature, combustion products, and its properties are acquired using GASEQ. The heat transfer losses include losses due to convection and radiation of the mixture. The hot jet from individual burner enters the preheater with a velocity, which in turn causes convection to occur from the gas to the surface of the preheater. The convection loss is predicted using basic convection heat transfer equation used for heat transfer of hot gases flowing over a plate. The radiation loss was predicted using the emittance of the combustion products at different temperatures using existing analytical data. The emittance of the mixture is a function of adiabatic temperature of the combustion, chamber pressure, and partial pressure of water vapour in the combustion product. The prediction is compared with experimental total temperature, and calculated using the chamber pressure PO. The predicted total temperature is also compared with thermocouple value in one of the tests. The prediction helps in the design of supersonic combustion experiments which are largely dependent on the total temperature of the preheater. The prediction was used get the total temperatures up to 1100 K in the preheater. © 2021, Springer Nature Singapore Pte Ltd.