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Roof Square Footage Calculator – Area, Squares, Bundles & Rolls
Use this free Roof Square Footage Calculator to estimate the size of your roof and translate it into roofing squares, shingle bundles, and underlayment rolls. Enter the house footprint, a uniform overhang, select the roof type (gable, hip, or shed), choose a pitch, and apply a waste factor. The tool also estimates ridge-cap length and drip-edge pieces so you can create a more complete materials list.
How to Use
- Pick your Unit System, Roof Type, and Pitch.
- Enter your house Length and Width (exterior wall-to-wall) and a uniform Overhang.
- Set a Waste allowance (10% is a common starting point).
- Adjust material coverage if needed: bundles per square, underlayment ft² per roll, ridge-cap LF per bundle, and drip-edge piece length.
- Click Calculate to see roof area (ft²/m²), roofing squares, bundles, underlayment rolls, ridge/hip length, and drip-edge pieces.
What’s a “Roofing Square”?
One roofing square equals 100 square feet of roof surface. Most 3-tab and architectural shingles are sold as 3 bundles per square, but always check your specific product. Underlayment rolls commonly cover about 400 ft² (≈ 37 m²) effectively after overlaps.
Formulas & Assumptions
- Plan area (with overhangs): (L + 2e) × (W + 2e), where e is uniform overhang.
- Slope factor (common rafter): SF = √(1 + (rise/12)²) (independent of units).
- Roof surface area: Aroof = Aplan × SF. Then add waste: A × (1 + waste%).
- Squares: ft² ÷ 100. Bundles: squares × bundles/sq (round up).
- Underlayment rolls: area ÷ coverage per roll (round up).
- Linear footage: gable/shed eaves & rakes use the plan perimeter with overhangs; ridge length for gable is the house length; hip roofs use ridge ≈ L − W (≥0) and four hips.
Results are estimates. Roof framing, ventilation, underlayment classes, ice and water shield, and fastener schedules vary — always confirm against local code and manufacturer instructions.
Related Tools
Plan your project with: Plywood Calculator, Concrete Calculator, Gravel Calculator, and Sand Calculator.
Important Estimate Disclaimer
The results provided by this calculator are intended as general estimates only and should not be considered precise engineering measurements. Actual material requirements, costs, and quantities can vary significantly based on site conditions, local building codes, soil type, reinforcement requirements, climate exposure, and the intended use of your project.
These calculators are designed to help you plan and budget your project more effectively, but they do not replace professional advice from a qualified contractor, engineer, or building inspector. Always verify your calculations and assumptions with trained professionals before placing material orders or commencing construction.
For more information on the assumptions, formulas, and data used in these tools, see our Data Sources and Methodology pages.
Material estimates, cost figures, and volume calculations are approximate and may not reflect your actual requirements. Always double-check dimensions and project-specific needs, and consider adding a contingency allowance for waste, over-excavation, and unforeseen conditions.
If you are unsure about any aspect of your project — including structural requirements, reinforcement needs, drainage, or load-bearing capacity — consult with a licensed professional before proceeding.