I don't measure inches. I measure the number of strips I need to cut.
The width of fabric is 40-42". Using 40", two strips would give you 80". That's enough for the 68", but not for the 93". I would cut 9 strips: 2 each for the top and bottom, 2-1/2 each for the sides. For fabric requirements, 9 strips at 2-1/2" means you need 22.5 inches.