I will be using this film for an eyebrow shaped transom which measures 60 inches long and 13 inches at highest point of arch. How do I calculate what I need?

Since the window is 60" wide, you have 2 options. You can seam the film going left to right which would require 3 feet, or you can turn the pattern sideways and order 5 feet. There would be no seam this way, but it would look different than the picture on the website. If you look in the reviews on the product page, you can see what that would look like.