Estimating Materials Using Perimeter
To estimate materials that are sold by the length, or lineal foot (edgings, flashing, etc.) divide the total lineal foot (perimeter) by the length of the product. To estimate the number of 12′ pieces of J-channel required to go around a structure with a 212′ perimeter divide the total perimeter by the per piece length, 12′.
212/12=17.66 (sell 18)