Revit uses room boundaries when computing the area, perimeter, and volume of a room. You can check room boundaries in plan views and section views.
To check room boundaries, you can select rooms or change visibility/graphic settings for the view. See Selecting a Room and Controlling the Visibility of Rooms.
When working with rooms, open a plan view and a section view, and click View tab
Tile Windows to tile the windows. This strategy allows you to see the perimeter of the room and its upper and lower boundaries at the same time.