To determine How many frame sets to purchase, divide the lenght of the greenhouse by four. The result is the number of spaces between the hoops. Then add one extra frame set to that fot the total sets required (CLICK ON MORE INFO FOR EXAMPLE)
If your greenhouse is to be 48 feet long then divide 48 by 4= 12 spaces, then add 1 extra frame set for the starter frame, So you will need 12+1= 13 Frame Sets