I'm making a table topper that is 45" x 45" square. I'm trying to use fabric that I already have for the backing & I have a piece that is 2 yards. Before I start cutting on it I would like to know if it's enough to use for the backing of this topper. I did find the site below that show that I could cut the backing fabric on the diagonal but not sure if this is the best thing to do yet. I've never made a diagonal backing before. I'm not a math whiz & don't want to mess this up. Thanks for your suggestions.
http://www.multi-patch.com/html/fabric_calc.php