Four simple steps to an accurate shingle estimate — no expertise required.
Use a tape measure or your building plans to find the length and width of each roof plane in feet.
Roof pitch is expressed as rise over 12. A "4/12" pitch means the roof rises 4 inches for every 12 inches of horizontal run.
Plug the length, width, and pitch into our calculator. Optionally adjust the waste factor (default is 10%).
Instantly see the total roof area, the number of shingle bundles, squares, and individual pieces you'll need.
The calculator uses a pitch multiplier derived from the Pythagorean theorem:
Pitch Factor = √(1 + (pitch ÷ 12)²)
Total Area = Length × Width × Pitch Factor × (1 + Waste%)
One roofing "square" covers 100 sq ft, and most three‑tab shingle bundles cover ⅓ of a square, so you need 3 bundles per square.