We envisioned creating an interface to perform, automate, and manage QM calculations with multiple software packages to solve these challenges. Several projects aim to automate computational chemistry, but either for a specific purpose or through a form of scripting. We had specific objectives for the interface: 1) Be user-friendly and intuitive; 2) Be open-source, customizable and expandable; 3) Be easy to use on multiple operating systems (OS); 4) Provide a suitable environment to learn computational chemistry; 5) Provide all the necessary tools to manage and analyze QM calculations; 6) Provide advanced functionalities for tasks which would otherwise be cumbersome to carry out. One software that approaches this vision is WebMO, 20 although it is not open-source and cannot be modified freely. To the best of our knowledge, there is no opensource project that embodied our vision and suited our needs. We report herein the details of CalcUS, our open-source, webbased computational chemistry platform.