How it works
Calculate your material requirement
Estimate sloped roof area, roofing squares, and three-tab bundle equivalents from footprint dimensions and roof pitch.
The formula
Sloped area = footprint area × √(1 + (pitch rise ÷ 12)²), increased by the selected waste allowance. One roofing square equals 100 ft².
Worked example
A 40 ft × 28 ft footprint with a 6:12 pitch has about 1,252 ft² of sloped area before waste and 1,377 ft² with a 10% allowance.
Before you order
- Measure overhangs when they are not included in the building footprint.
- Complex hips, valleys, dormers, and intersecting roofs should be divided into surfaces.
- Bundle coverage varies by shingle product; use the manufacturer's coverage.