Roof Area Calculator
Calculate true roof surface area from building size and roof pitch angle.
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How to use
- Enter the building length and width.
- Enter the roof pitch angle — take it from the design or measure it on the existing roof.
- Enter the overhang (eaves) on all sides in inches.
- The true sloped area, including wastage, appears automatically.
Note: This formula gives a good estimate for both gable and hip roofs because their sloped area equals plan area x slope factor. For complex roofs (with many valleys), split the roof into sections and calculate each one.