Roofing Calculator

Accurately estimating roofing materials starts with understanding how roof pitch affects the actual surface area. A flat footprint of 1,200 sq ft becomes significantly larger once you account for slope — a 6/12 pitch adds roughly 12% more area. This calculator takes your roof's footprint dimensions (or total area), your pitch expressed as rise per 12 inches of run, and a waste percentage, then computes the true sloped area you need to cover.

Roofing is sold in squares (100 sq ft each) and asphalt shingles typically come in bundles of roughly one-third of a square. By factoring in your chosen waste allowance — usually 10–15% for simple roofs and 15–20% for complex ones with hips, valleys, and dormers — this tool gives you the exact number of bundles to purchase so you avoid costly shortages or excessive leftovers.