The size appears slightly less than 70"x90". One would want to mock this up to test the clearance of the two tracks at the top of the diagram. Operating two trains on this layout may result in the engine cab overhang on the inner loop interfering with a train on the outer part of the loop. It may need a half straight on each side to get more clearance at the top for two train operation. With one train it looks great, but it does require a good size footprint. In our home I would add a second independent loop around the outside to prevent the "children" from arguing over whose turn it is to run the train. That would make the size just under 80"x100".