Roof Area Calculator
Calculate the total roof area based on building dimensions and roof pitch. This tool helps estimate materials needed for roofing projects.
Published by:
isCalculator Editorial Team
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How to Use the Roof Area Calculator
This calculator estimates the total roof surface area (in square feet) for a simple gable or flat roof. It accounts for building dimensions, roof pitch, and overhang.
- Enter Building Length (ft) – The length of the building’s footprint, e.g., 40.
- Enter Building Width (ft) – The width of the building’s footprint, e.g., 30.
- Enter Roof Pitch – The rise per 12 inches of run, e.g., 4 for a 4/12 pitch. Use 0 for a flat roof.
- Enter Overhang (ft) – The roof extension beyond the walls on all sides (default is 0).
- Click Calculate Roof Area.
The result shows the total area in square feet, along with the formula breakdown: (Length + 2×Overhang) × (Width + 2×Overhang) × sqrt(1 + (Pitch/12)²).
All inputs must be positive numbers (pitch and overhang can be zero). Use feet for all dimensions.
Previous Results
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Frequently Asked Questions
Roof pitch is the slope expressed as a ratio of vertical rise to horizontal run, e.g., 4/12 means 4 inches rise per 12 inches run.
Overhang is the extra length of roof extending beyond the building walls. It adds to the effective dimensions for area calculation.
Yes, set the pitch to 0 for flat roofs. The calculator will compute the area without slope factor.