Obtaining high-accuracy chemical species thermochemistry is essential to solve many important problems in chemistry. Experiments can provide high-accuracy results, sometimes even achieving an accuracy of 0.1 kcal/mol or better especially for small, closed-shell species. However, usually multiple experiments need to be combined to obtain accurate thermochemical parameters reported in standard states. Moreover, many species (especially radicals, but not exclusively) cannot be isolated conveniently for experimentation. Due to the importance of these parameters, several databases exist that provide high-accuracy thermochemistry data. One widely used database is the Active Thermochemical Table (ATcT), which aims to produce a self-consistent set of species thermochemistry obtained from theoretical calculations and experiments with continually improving accuracy. When data from the ATcT or other high-quality experimental sources are available, they represent the preferred route for obtaining the most accurate thermochemical values of a species of interest. However, entries in ATcT represent only a minuscule fraction of all species of interest in the vast chemical universe. Given that experiments are often time-consuming, particularly if they require synthesizing the species of interest, computing species thermochemistry through quantum mechanical (QM) calculations can prove quite valuable.