thank you krafty14 and quiltingshe! I looked at the Robert Kaufman quilting calculator and there was one review that was negative that has scared me from purchasing it.
I have decided to purchase some minky that is 90 inches wide so that my back will not have a seam. It will cost me 20.00 a yard but I will only need two yards. I will not have to do the sewing. The store that I'm buying the back from will also sew my quilt. It's called "Quilts on the Corner" they only do quilting from edge to edge, you can choose designs that fit your quilt. Here is the website!
http://www.quiltsonthecorner.com/