This project aims at developing an educational tool, named REAJA, for simulating ideal chemical reactors according to the continuous stirred‐tank reactor, plug flow reactor, and batch reactors. The software was developed using the Python programming language, following the Agile methodology and test‐driven development. It has a main interface that introduces the objective and its functionalities through the images, texts, and buttons for three reactor modules: isothermic, adiabatic, and with the thermal exchange. Initial concentration, equilibrium constant, and reaction rate constant can also be calculated by specific modules. We present the results in a separate screen containing comparative graphs of concentration, temperature, and conversion, allowing the user to choose the best option among the simulated reactors. The software Aspen Plus and Excel/Runge–Kutta fourth‐order method was applied to verification testing with REAJA obtaining <5% and 10–90%, respectively. The last case could be justified by the simplifications made for educational purposes. Finally, the software was applied at the minicourse of the 21st week of Chemical Engineering of UNICAMP and in the undergraduate course of Topics in Chemical Processes with problem‐based learning methodology. We use a questionnaire to validate the usefulness of our software, which results are promising and indicate the success of our educational tool as a complement in the classroom since it facilitated the understanding of contents related to kinetics, thermodynamics, and chemical reactors.