Roofing calculator
Published On: 02/03/2026
Roofing Calculator
Estimate roof area and material needs (shingles, underlayment, and bundles) using basic roof dimensions. This calculator supports common roof shapes and adds an optional waste factor.
Inputs explained:
• Roof shape: choose the closest match (rectangular, gable, hip approximation).
• Building length & width: footprint dimensions (outside-to-outside).
• Roof pitch: slope of the roof (e.g., 4/12). Used to convert footprint to sloped roof area via a pitch multiplier.
• Eave overhang (optional): extra roof projection beyond walls, added on both sides.
• Waste factor: extra percentage for cuts, starter strips, valleys, and mistakes (often 10–15%).
• Roof shape: choose the closest match (rectangular, gable, hip approximation).
• Building length & width: footprint dimensions (outside-to-outside).
• Roof pitch: slope of the roof (e.g., 4/12). Used to convert footprint to sloped roof area via a pitch multiplier.
• Eave overhang (optional): extra roof projection beyond walls, added on both sides.
• Waste factor: extra percentage for cuts, starter strips, valleys, and mistakes (often 10–15%).
Added to length & width on both sides.
1 “square” = 100 ft².
Tip: Roof complexity (valleys, dormers, steep pitch) can increase waste. Always verify with your contractor/material supplier.
Roofing Calculator — Description
The Roofing Calculator estimates your roof’s total surface area based on building length, width, roof pitch, and optional overhang. It applies a pitch multiplier to convert footprint area into sloped roof area and adds an optional waste factor to account for cuts, valleys, and starter strips. The calculator also estimates the number of roofing squares (100 ft²) and shingle bundles needed.
Use this tool for planning material quantities before purchasing shingles, underlayment, and related roofing supplies.