Roofing Calculator — Squares, Bundles & Cost
Enter the building footprint and roof pitch to get true roof area, squares, bundles and an installed cost range.
Your numbers
Results
- Roof areapitch multiplier 1.118
- 1,409 sq ft
- Squares to order12% waste included
- 15.8 sq
- Shingle bundles3 bundles per square
- 48 bundles
- Installed cost
- $7,455 – $9,940
- Underlaymentsynthetic, 4 squares per roll
- 4 rolls
- Ridge cap
- 42 lin ft
- Drip edge
- 15 pcs (10 ft)
- Roofing nails
- 4 boxes (50 lb)
Quantities are estimates for planning. Verify spans, spacing and local amendments before ordering.
How the math works
- True roof area = footprint (including overhangs) × pitch multiplier, where the multiplier is √(rise² + 144) ÷ 12.
- One roofing square = 100 sq ft = 3 bundles of standard architectural shingles.
- Waste runs 10% on simple gables and 15–20% on hips, valleys and cut-up roofs.
Code & best practice
- IRC R905.2 requires a minimum 2:12 pitch for asphalt shingles, with double underlayment below 4:12.
- Ice-and-water shield is required from the eave to 24" inside the warm wall in cold-climate jurisdictions.
- Most jurisdictions allow only two shingle layers before a full tear-off is required.
Frequently asked questions
How many squares is a 40x28 roof?
At a 6/12 pitch with 12" overhangs, roughly 15 squares of actual roof area, or about 17 squares ordered with waste.
How many bundles of shingles per square?
Three bundles per square for standard architectural shingles; some heavyweight products use four.
How much does a new roof cost?
Asphalt shingle replacement typically runs $450–$700 per square installed, including tear-off and disposal.