Roofing Area Calculator
Calculate the total roof area and material needs for a simple gable or flat roof. Enter dimensions and pitch to estimate roofing squares, shingles, and cost.
Published by:
isCalculator Editorial Team
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How to Use the Roofing Area Calculator
This calculator estimates the total roof area, number of roofing squares, shingle bundles, and cost based on your roof dimensions and pitch. All measurements are in feet (imperial).
- Enter Length & Width – Input the roof’s length and width in feet (e.g., 40 and 30). Use decimal values if needed.
- Select Pitch – Choose the roof pitch from the dropdown (e.g., 6/12 for a standard slope). This adjusts the area for the roof’s angle.
- Set Waste Percentage – Enter a waste factor (default 10%) to account for cuts and overlaps. Must be between 0 and 50.
- Enter Cost per Square – Input the price per roofing square (100 sq ft) for shingles (e.g., $100).
- Click “Calculate” – The results will show:
- Total Roof Area (ft²) – the actual surface area including pitch.
- Roofing Squares – area divided by 100 (standard unit for roofing).
- Shingles Needed – bundles (3 per square).
- Estimated Cost – based on your cost per square.
Tip: Use the formula shown below the results to understand the calculations.
Previous Results
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Frequently Asked Questions
Roof area is calculated by multiplying length and width, then multiplying by a pitch factor based on roof slope. The pitch factor accounts for the increased surface area due to slope.
A roofing square is 100 square feet of roof area. It is the standard unit used by roofing contractors to estimate materials and cost.
Typically, three bundles of shingles cover one square (100 sq ft). However, this can vary by shingle type; always check manufacturer specifications.