How to Calculate Roofing
What is Roofing?
A roofing calculator estimates the material needed to cover a roof, accounting for the pitch (slope) which increases actual roof area beyond the building footprint. Roofing material is measured in "squares" — one square covers 100 square feet.
Step-by-Step Guide
- 1Measure the building footprint: length × width
- 2Calculate pitch factor: √(1 + (rise/run)²) where run is typically 12"
- 3Actual roof area = footprint × pitch factor × (number of roof sections)
- 4Add 10–15% waste for ridge caps, valleys, and cuts
- 5Divide by 100 to get squares; multiply by 3 for shingle bundles
Worked Examples
Input
40×30 ft house, 6/12 pitch, 15% waste
Result
~15 squares, 45 bundles
Pitch factor: √(1+0.25) = 1.118
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