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Roofing Calculator
Estimate roof area from the house footprint and pitch, then roofing squares, shingle bundles, underlayment and cost.
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How to use it
- Enter the footprint of the house and the eave overhang.
- Choose the roof pitch (rise per 12 in of run).
- Add 10% waste for simple gable roofs, 15% for hips and valleys.
How it works
Roof area = (length + 2 × overhang) × (width + 2 × overhang) × pitch factor, where the factor = √(1 + (pitch ÷ 12)²) - e.g. 1.118 for 6/12. A roofing square is 100 ft²; standard architectural shingles come about 3 bundles per square. Felt or synthetic underlayment rolls usually cover 4-10 squares - check the roll.
FAQ
How many bundles of shingles are in a square?
Usually 3 bundles for standard architectural shingles; some heavier products need 4.
How do I measure roof pitch?
Hold a level horizontally from the roof surface; measure 12 in along it, then the vertical rise to the roof. 6 in of rise = 6/12.
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