Hi @Toni,
Generally speaking I think it’s safe to say that there is just one major reason for creating a Calculated Column and that is if you need to place the calculated results in a slicer, or see results in rows or columns in a table (as opposed to the values area), or in the axes of a chart.
The value of a calculated column is stored in the data model and is computed during data refresh time and uses the current row as a context; it does not depend on user interaction in the report. A measure operates on aggregations of data defined by the current context, which depends on the filter applied in the report – such as slicer, rows, and columns selection in a table, or axes and filters applied to a chart.
Read more here.
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For this type of calculation you would use a Measure and for more details on Grouping/Segmentation with supporting tables please see this topic by @Greg
I hope this is helpful