I am getting ready to begin my first Jacob's Ladder and have no idea how much fabric to purchase. Here is a shot of my design:

Click image for larger version.  Name: Jacob's Ladder.jpg  Views: 25  Size: 90.0 KB  ID: 19091

Finished size will be 96" x 108" after border is attached. It will be four different fabrics like in this design however in a beige/tan/brown color. How do I go about figuring fabric to purchase?