Calculations open up amazing possibilities in Tableau. You are no longer confined to the fields in the source data. With calculations, you can extend the data by adding new dimensions and measures, fix bad or poorly formatted data, and enhance the user experience with parameters for user input and calculations that enhance the visualizations.
The key to using calculated fields is understanding the four main types of calculations in Tableau. Row-level calculations are performed for every row of source data. These calculated fields can be used as dimensions or they can be aggregated as measures. Aggregate-level calculations are performed at the level of detail that's defined by the dimensions that are present in a view. They are especially helpful, and even necessary, when you must first aggregate components of the calculation before performing additional operations...
