First off I want to make sure it is clear that I am not saying “never use calculated columns.” I am not. What I am saying is they should be avoided, and there are several reasons. I am going to focus on the model size, and thus performance. Note that the data I am going to show is a contrived set of data for demonstration purposes only to explain.
Read the whole thing, including a set of questions you might want to ask yourself before deploying that PBIX file with calculated columns in it.