You can create DAX measures in your Power BI report. As of today, you can only create DAX calculated measures in Power BI through the Desktop and by Importing the data into the report.
Access Power BI Desktop. Click Get Data from Home menu > SQL Server Analysis Services Database. Type your connection information. Then choose “Import Data” instead of “Connect Live”:
Login with your or other credentials:
Choose from the set of columns to add to your model:
From the Home Menu > Choose New Measure > New Measure > Then go to the DAX measure formula bar below the home menu and type your measure the same way you would do in PowerPivot or in SSAS Tabular: