g2server wrote in answer to the question 64 bit Microsoft SQL Server Data Tools on Stack Overflow:
As the others have said, there is only a 32 bit version.
The important thing is, if you’re running an x64-based SQL instance (64-bit), make sure to select “New Instance” on the Installation Type page, and NOT “Add features to an existing instance”. Not doing so will cause it to error out.
Community Wiki answer to document the solution on Stack Overflow found by Dave