Roofing & buildingFree calculator
Estimate the materials for a new shingle roof. Enter the roof footprint and pitch to get the true roof area, roofing squares, bundles of shingles and the extras you need.
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How to measure
- Measure the length and width of the house, including roof overhangs.
- Find the pitch: the rise in inches for every 12 in of run (for example 6/12).
- For complex roofs, add 15% waste instead of 10%.
The formula
Roof area = footprint × pitch factor Pitch factor = √(1 + (rise ÷ 12)²) Squares = area ÷ 100 sq ft · Bundles = squares × 3
Worked example
A 40 × 30 ft footprint at 6/12 pitch has a roof area of 1,342 sq ft. With 10% waste that is 14.8 squares, or 45 bundles of shingles.
Tips before you buy
- Most 3-tab and architectural shingles come 3 bundles to a square.
- Roof work is dangerous. Use fall protection or hire a pro for steep roofs.
- Check local codes for underlayment and ice barrier requirements.
Frequently asked questions
What is a roofing square?
A roofing square is 100 sq ft (about 9.3 m²) of roof surface.
How many bundles of shingles per square?
Usually 3 bundles, though some heavy architectural shingles need 4.
How do I find my roof pitch?
Hold a level 12 in out from the roof surface and measure straight down to the roof. That measurement is the rise per 12.
Results are estimates for planning only. Always check quantities with your supplier before you buy.