Octagon calculator for growers thinking about building a stadium.

I have been looking into building a stadium system and came across this calculator for figuring measurements of an octagon and thought it might help someone else out. My thoughts are building two halfs of an octagon that are connected by a hinge so it can be opened up for easy access or maybe just one or two sides of the octagon to make a door. I want a 360 grow and still have easy access so each level will have to have two seperate sections so it can open up. The stadium/vertical grow has been done by some other growers on here and I really like the concept.
http://www.pagetutor.com/octagon_layout/index.html

Thanks man this helped a lot +rep