It's tough to dictate the finished size. The best I could come up with is 640" of 2 1/2" fabric. This would sew up in these rounds (considering finished size of 2" for length), with a finished size of 32" x 40". I'd start with some extra length, because when I did this I found it difficult to get clean cuts when I ended a seam. I had to straighten my edges.
Round 1 4" length x 320" width
Round 2 8" length x 160" width
Round 3 16" length x 80" width
Round 4 32" length x 40" width.
If I needed 36" x 40", I think I would make the above, and then add two additional strips.