Metal Roofing Calculator
Calculate how many metal roofing panels you need for any roof size and pitch.
Estimate coverage for standing seam, corrugated, and R-panel metal roofing with waste factors.
Why Metal Roofing? Metal roofing lasts 40–70 years versus 20–30 for asphalt shingles. It reflects heat (reduces cooling costs), withstands wind up to 140 mph, and is fire resistant. Common in commercial and agricultural buildings — increasingly popular for residential use. Standing seam is the premium option; corrugated and R-panel are common for barns and commercial.
Panel Types and Coverage Standing seam: hidden fasteners, 12"–18" wide panels, “flat” look between seams. Premium option. Corrugated metal: exposed fasteners, traditional wavy profile, 26" total width with 24" coverage. R-panel (PBR panel): exposed fasteners, rib profile, 36" total width with 36" coverage. Coverage width ≠ panel width — panels overlap, so effective coverage is less than nominal width.
Roof Pitch and Slope Factor Roof pitch is expressed as X:12 (rise over run). A 4:12 pitch rises 4 inches for every 12 inches of run. Slope factor = √(1 + (rise/12)²) A 4:12 pitch has slope factor 1.054 — about 5.4% more material than a flat surface. Always measure the plan (horizontal) area and apply the slope factor, not the actual surface.
Calculating Roof Area Gable roof: plan area = (length × width). Total roof area = plan area × slope factor × 2 sides. Hip roof: more complex — treat as four panels and sum. Always add eave overhang to roof dimensions (typically 1"–2" per side).
Waste and Overage Standard waste: 10% for simple roofs, 15–20% for complex roofs with many hips/valleys/penetrations. Always order at least 10% extra — metal panels cannot always be easily matched later. Panel lengths: typically 8, 10, 12, 16, or 20 feet. Longer panels = fewer seams = less leakage risk.
Fasteners Standing seam: 1 clip per panel per purlin. Clips hidden under seam. Exposed fastener panels: screws at each rib, every 12"–24". Count roughly 80–120 screws per square (100 sq ft). Use self-drilling hex-head screws with EPDM washer — prevents water intrusion.