Methods, systems, and media are provided for using a calculator application to calculate answer values by evaluating formulas based on user input. The calculator application is hosted by an operating system and includes a template store containing templates that define user interface elements such as input fields associated with variables. The templates also have embodied therein formulae that define relationships between the variables. A user-interface, generated from information in a template, is provided to a user that includes input fields for receiving values to be associated with variables. Answer values are calculated by evaluating the formulae based on user input.