What you need to do is to make a list of each piece of wood with length, width and thickness.
I'm afraid that's only going to get you close, and not the exact number. Almost without any doubt there will be waste, and quite a bit of it.
Just looking at the square footage, and assuming a thickness of one inch, you have somewhere around 30 square feet. I just did a very quick guesstimate in my head, so that's not going to be dead on.
I would be ordering at least 40 board feet if I had 30 square feet of product.
OK, fess up...which one of you clowns stole my sig? It was right here a second ago.