Regarding interest in and concerns about high efficiency in recent times, an irreversibility assessment of energy conversion systems is significant. Turbojets, a type of energy conversion system, are widely used to provide thrust for aerial vehicles, such as military aircraft missiles, commercial aircraft and so on. From this point of view, the current study aims to introduce a comprehensive irreversibility assessment methodology exemplification for a turbojet. First of all, a basic irreversibility assessment methodology is explained with an application. Following this, a comprehensive assessment is performed. Within this framework, a number of a novel measures are defined by derivations in addition to previously well-known indicators. These measures are beneficial for the decomposition of the irreversibility in a turbojet and its components. At the end of the study, the highest endogenous irreversibility is determined to be in the turbine component of the turbojet engine whereas the highest avoidable irreversibility is found to be in the compressor component of the turbojet engine. The current paper is considered to be of use for researchers and scientists interested in aero-engine performance, thermal engineering and aerospace engineering. (C) 2018 National Laboratory for Aeronautics and Astronautics. Production and hosting by Elsevier B.V.