This paper provides a methodology developed for the calculation of the feed rate and of the exit air conditions in an adiabatic rotary dryer, which operates with granular, non-porous solids having only unbound surface moisture. Some aspects related to the algorithm are also discussed in greater detail, such as the behavior of the wet-bulb temperatures along the dryer and the selection of initial values for the iterative loops. The results have been compared with published data from commercial rotary dryers, and predictions compare within 10% of the available data. The methodology can be used to evaluate trends in the behavior of a rotary dryer where the operating parameters vary, and it is useful for the practical engineer, who has to manage several problems commonly encountered in the operation of a rotary dryer installed in a chemical plant