If you're buying 54" wide material or 45" wide material, you need to figure out how many panels.....
108" = 3yds
54 wide fabric ~ 2 panels x3 yd=6 yds fabric + a bit extra - I'd get 6 1`/2 yds
45 wide fabric ~ 3 panels x 3 yds = 9 yds fabric + bit extra - 9 1/2 or 9 3/4 yds fabric depending on the extra needed
give or take....,but gets me close