MCycle allows users to analyse thermodynamic power cycles and their individual components, as well as size cycle components to defined cycle design parameters. It was developed due to a need for an open source tool with easy scripting for sizing heat exchangers that would allow control over individual component parameters. Users may now analyse a growing collection of thermodynamic power cycles and cycle components, including heat exchangers, expanders, compressors, heaters and coolers. Each type of component has models of varying complexity, allowing MCycle to be equally applicable to simplistic cycle analyses as to detailed sizing optimisations. The project source code is found at https://github.com/momargoh/MCycle and the documentation is hosted at https://mcycle.readthedocs.io.