How metal roofing panels are calculated
Eave length divided by panel width, rounded up. A 40 ft eave with 3 ft wide panels needs 14 panels (40 / 3 = 13.33, rounded up). Each panel runs from eave to ridge, so its length is the slope length — a 12 ft run at a 30 degree pitch has a slope length of 13.86 ft.
Exposed-fastener panels are usually 3 ft wide; standing-seam panels are often 12 to 18 inches wide. Confirm the width with your supplier before ordering, and add one spare panel for cuts and mistakes.
Need shingles instead, or the roof area itself? Try the shingle calculator or the full roofing calculator.