I think your six yards is way too much. Yes, there is an app for that but... First, how wide is the fleece you want to buy? most fleece is about 60 inches wide and by the time you take away the edges, you have about 58 inches of usable width. since the measurement on the quilt top is more than 58 inches both ways, you will have to piece it. The amount I figured out is that you'll need to purchase four yards for the measurement you gave in your message and with 60 inch wide fleece. Some fleece is only 54 inches, and you'll still need the four yards but will have less waste. These calculations are for a seam in the fleece across the width of the quilt and not down the length of the material. If you want a seam down the length instead, then you would need the 6 yards with a lot of waste.