Metal Roofing Calculator

Panels Needed is set by three inputs acting together: Roof Width and Panel Width determine how many panel widths fit across the eave (each panel effectively covers Panel Width minus 1 inch of overlap), and Waste Factor scales that count up for cuts and trim. Roof Length and Roof Pitch play no part in that count at all. Ridge Cap is the mirror case -- it is simply the rounded Roof Length in feet, because the ridge line runs the full length of a gable roof, so Roof Width, Panel Width, Roof Pitch, and Waste Factor leave it completely unchanged. Actual Roof Area corrects the flat footprint (Roof Length times Roof Width) for the extra surface pitch adds, using the standard slope factor sqrt(1 + (pitch/12)^2) -- a 4:12 roof adds about 5% more surface than its footprint, a 12:12 roof (45 degrees) adds about 41%.

Metal Sq Ft, the total metal ordered, responds most to Roof Width, but through a single indirect mechanism, not a direct area term: Roof Width does not appear in the Metal Sq Ft formula on its own, only inside Panels Needed's rounding-up calculation, so widening the roof moves Metal Sq Ft only when it's enough to push the panel count up a whole step -- small width changes that don't cross a rounding step leave Metal Sq Ft completely unchanged. Waste Factor and Panel Width have smaller, partially self-cancelling effects on Metal Sq Ft, since a wider panel needs fewer of them to cover the same width. This calculator does not account for hips, valleys, dormers, or penetrations, which add trim and waste beyond the flat Waste Factor percentage.