Calculate the fabric needed to drape a ceiling in two parts. Measure the length of the room and divide that measurement by two.
Take the measurement figure and add 20 percent. This is the amount of fabric needed per panel for one length side of the center ring.
Measure the width of the room and divide that number by two. Add 20 percent to the divided number for the amount of fabric needed per panel for one width side of the center ring.
Determine the width of the fabric and how many widths will fit the length of the room. Multiply this by two. Determine how many widths will fit the width of the room and multiply this by two. These measurements will tell you how many panels you need of length and width sizes.