CalculynHow it works
A sloped roof has more surface than the floor beneath it. Multiplying the footprint by the pitch multiplier gives the true roof area. Roofers sell in squares (100 sq ft), and most shingles come 3 bundles per square.
Formula
Roof area = Footprint × √(1 + (rise ÷ 12)²) Squares = Roof area × (1 + waste) ÷ 100
Example
A 2,000 sq ft footprint at 6/12 pitch: 2,000 × 1.118 = 2,236 sq ft; with 10% waste ≈ 24.6 squares, 74 bundles.
Assumptions & limitations
- Simple gable or hip roof with one pitch.
- Excludes ridge caps, starter strips and underlayment.
Frequently asked questions
How do I find my roof pitch?
Measure how many inches the roof rises over 12 inches of horizontal run. A 6-inch rise is a 6/12 pitch.