Enter the length and width of your roof's footprint (the rectangular area as seen from above), the roof pitch, and your shingle type. The calculator adjusts the flat footprint area for the actual sloped surface area, then converts to roofing squares and bundles. It also estimates nails needed and includes a 15% waste factor for cuts, valleys, and starter courses.
Roof pitch is expressed as "rise per 12 inches of run." A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. The steeper the pitch, the more surface area your roof has compared to its footprint. A 6/12 pitch adds about 12% more surface area; a 12/12 pitch adds 41%. Our calculator handles this automatically.
A roofing square equals 100 square feet of roof area. All roofing materials are priced and sold by the square. For 3-tab asphalt shingles, you typically need 3 bundles per square. Architectural (dimensional) shingles are thicker and require about 3.5 bundles per square. Standing seam metal roofing is ordered by the square.
Every roofing job generates waste — cut pieces at valleys and hips, damaged shingles, and starter courses. For a simple gable roof, add 10–15%. For complex roofs with multiple valleys, dormers, or hips, add 15–20%. Our calculator shows both exact and waste-adjusted totals.
A 1,000 sq ft roof equals 10 squares. For 3-tab shingles, you need 30 bundles. For architectural, about 35 bundles. Always add 10–15% for waste.
A square is 100 square feet of roof area. Roofing materials are sold by the square. One square of 3-tab shingles typically requires 3 bundles.
Yes. A steeper roof has more surface area than a flat one with the same footprint. Our calculator adjusts for pitch using a slope multiplier.
Add 10–15% for waste on a simple gable roof. For complex roofs with valleys, dormers, or hips, add 15–20%.