This paper presents a comparison of the Stirling and Ericsson processes. At the beginning of the paper, the theoretical foundations of circular processes in general are given, and elementary circular processes are given. Circular processes are used to convert thermal energy into mechanical energy. They consist of state changes such as isochores, isobars, isotherms, adiabats, and polytropes. In the second part, the Stirling and Ericsson circular processes are explained in detail, the equations for the calculation of the characteristic states and sizes of the process are given, and the images characteristic for a particular process. Also, the ideal processes are compared with real processes, and images of the motors working on these processes are given. The task was to computationally compare the two processes and analyze the obtained results. Three comparisons were made, according to the heat input, the compression ratio and the maximum temperature in the process. The analysis found that Ericsson's process, which is very similar to Stirling's circular process, achieves a lower degree of action and the resulting work. At the end, diagrams and tables with characteristic quantities are given, in which one can see the difference between the obtained results.