[Changing the scale of objects in a drawing]

I am creating a floorplan for several rooms and it is important that I know the precise room size when I am locating fixturing. So I want to change the scale so that when I draw an object, instead of the actual size on the page I can scale them so it will show the dimension of the object. In other words, I simply want to change the scale where for example, 1 inch equals 2 feet so if I draw a rectangle that is 1" x 1", it will show as 2' x 2'. How do I do this?