Use a plan view to visually check the outer boundaries (perimeter) of a room.
By default, Revit computes the room area using the wall finish as the outer boundary. You can specify the wall center, wall core layer, or wall core center as the outer boundary. See Changing the Room Area Boundary Location.
If you need to change the boundaries of a room, change the Room Bounding parameter for model elements, or add room separation lines. See Room-Bounding Elements and Room Separation Lines.
If a room has sloped walls, ceilings, or other surfaces, you can check a section view to determine whether Revit is measuring the room perimeter at the appropriate height. See Computation Height.