Roofing Calculator
Estimate the number of roofing shingles, underlayment, and nails needed for a roof project based on roof dimensions and waste factor.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Roofing Calculator
This calculator estimates the materials needed for a roof based on its 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).
- Select Pitch – Choose the roof’s slope (rise per 12 inches). Options range from 2/12 (low) to 12/12 (steep).
- Set Waste Factor – Default is 10%. Adjust between 0% and 100% for material waste.
- Click “Calculate” – The tool computes the roof area using the pitch factor and applies the waste percentage.
- Review Results – You’ll see:
- Shingles – Number of bundles needed (1 bundle ≈ 33.33 sq ft).
- Underlayment – Rolls required (1 roll ≈ 400 sq ft).
- Nails – Pounds of nails (2.5 lbs per 100 sq ft).
All results are rounded up to ensure sufficient materials. Check the formula summary below the results for details.
Previous Results
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Frequently Asked Questions
Measure the length and width of your roof from the ground using a tape measure. If you cannot access the roof, use house dimensions and add overhangs.
The pitch factor accounts for the slope of the roof. It is calculated as the square root of (rise/12)^2 + 1, where rise is the vertical rise per 12 inches of horizontal run.
A typical waste factor is 10-15% to account for cutting, trimming, and mistakes. Steeper roofs or complex designs may require higher waste.