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Geometry & Practical Projects

Roof Area Estimator

Estimate roof surface area, roofing squares and shingle bundles from the building footprint, overhang and pitch.

Your inputs

Results

Roof surface area

1,502.6 ft²

Including waste
1,652.9 ft²
Roofing squares (incl. waste)
16.53
Shingle bundles
50
Roof area in m²
139.6

≈Estimate based on the stated model and assumptions

Notes for this result

  • Assumes a simple gable or hip roof where every plane has the same pitch. Dormers, valleys and complex roofs need a measured take-off.

What this calculator does

Roofing is ordered in “squares” of 100 ft². Pitch makes the roof surface larger than the footprint.

Formula and method

Plan area = (length + 2 × overhang)(width + 2 × overhang); roof area = plan × √(1 + (pitch ÷ 12)²); squares = area × (1 + waste) ÷ 100

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Building length: 40 ft
  • Building width: 30 ft
  • Eave overhang on each side: 1 ft
  • Pitch (rise per 12 run): 6
  • Waste allowance: 10 %
  • Bundles per square (100 ft²): 3

Results

  • Roof surface area: 1,502.6 ft²
  • Including waste: 1,652.9 ft²
  • Roofing squares (incl. waste): 16.53
  • Shingle bundles: 50
  • Roof area in m²: 139.6

How to read the results

Three bundles per square is common for standard shingles.

Assumptions and limitations

  • Complex roofs with dormers and valleys need a measured take-off.

Quantities and costs are planning estimates. Add sensible allowances, and check with suppliers, carriers or professionals before buying, shipping or building.

Questions

What is a roofing square?

100 square feet of roof surface.

Methodology and verification

Result type
Estimate based on the stated model and assumptions
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

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