I always draw a little sketch of the backing and quilt top to help visualize what I need when I'm buying fabric. When I use fabric from my stash, I lay the backing and top on the floor together to see what I need to do. I hate to figure out the math, too and would rather use a visual approach. However, I do use a calculator to figure the binding and Sparky gave you the info for that! Good luck and don't stress!