Construction tools
Roofing Calculator
Estimate simple gable roof surface, roofing squares, and shingle bundles using product coverage you enter.
Roofing material estimate
Enter the horizontal roof plan dimensions including overhangs, the rise per 12 inches of run, and coverage from the selected shingle bundle.
How the roof estimate works
For a simple symmetrical gable, the calculator uses √(1 + (rise ÷ 12)²) and plan area × slope factor. A roofing square is 100 square feet.
Bundle coverage and acceptable applications come from the exact shingle wrapper or manufacturer instructions; packaging varies by product.
Method & sources
The allowance is applied after excluded roof area, then bundles are rounded up using the entered coverage.
Important limits
- Only a simple gable plan is represented; hips, valleys, dormers, overhangs, irregular facets, and field measurements require a roof takeoff.
- This is not a roof design, structural check, fall-protection plan, or code-compliance determination.
- Confirm slope limits, deck, underlayment, flashing, ventilation, fastening, warranty, and quantities with local professionals and product instructions.
Reviewed references
- Owens Corning: DIY Roofing: Re-Roofing Tips
Reviewed 2026-07-21. Defines a roofing square as 100 square feet and explains bundle and allowance estimating as product/project dependent.
- GAF: Timberline HDZ Shingle Installation Instructions
Reviewed 2026-07-21. Product example showing that bundle coverage and permitted roof slope come from the selected manufacturer instructions.
- Inch Calculator: Roofing Material Calculator
Reviewed 2026-07-21. Competitive research only: informed the pitch-factor, roofing-square, and bundle result flow.