Roofing Calculator
Estimate the true surface area of a gable roof from the building footprint and roof pitch. The pitch multiplier accounts for the slope, then the material estimator converts area into roofing squares, shingle bundles and cost, with an optional 10% waste allowance for cutting and overlaps.
TheCalculators — Roofing Calculator
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Roof Area
1,453 sq ft
1,300 sq ft footprint × 1.118 pitch multiplier (6/12, 26.6°)
Material estimate
- Footprint
- 50 × 26 ft = 1,300 sq ft
- Pitch
- 6/12 (26.6°)
- Pitch Multiplier
- 1.118
- Roof Surface Area
- 1,453 sq ft
- With 10% Waste
- 1,599 sq ft
- Roofing Squares
- 14.53
- Squares incl. Waste
- 15.99
- Shingle Bundles (3/sq)
- 48 bundles
Pitch multiplier table (this footprint)
The estimate assumes a simple gable roof — complex hips, valleys and dormers need each plane measured separately. One roofing square = 100 sq ft; three bundles cover one square of standard 3-tab shingles.
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Formula
Roof Area = footprint × √(rise² + 12²) ÷ 12 · squares = area ÷ 100 · bundles = squares × 3 × (1 + waste)
Pro tips
- • Pitch multiplier for 6/12 is 1.118 — an 18% bigger roof than the footprint suggests.
- • Add 15% waste for hip roofs and complicated layouts.
FAQ
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