CALculation of PHAseDiagram-type (CALPHAD-type) thermodynamic databases for Mg alloy systems have been developed over the last two decades. In the present study, recent updates of the thermodynamic data related to the Mg-RE and Mg-Sn based systems to the FactSage FTlite database are reviewed. Several examples of applications of the new database to Mg alloy design are presented.