🏠Roofing Calculator: Squares, Bundles & Underlayment
Measure the footprint, pick your roof pitch, and get squares, shingle bundles and underlayment in seconds.
Your roof
You'll need
45 bundles
14.8 roofing squares · pitch factor 1.118
Roof area
1342 sq ft
Squares
14.8
Bundles
45
Underlayment rolls
4
Roofs steeper than 6/12 get tricky fast. Stay safe — harnesses aren't optional up there!
How it works
- Footprint = length × width (include overhangs)
- Pitch factor = √(1 + (rise ÷ 12)²)
- Roof area = footprint × pitch factor
- Squares = roof area × (1 + waste) ÷ 100
- Bundles = squares × 3 (for standard 3-tab or architectural shingles)
- Underlayment rolls = squares ÷ 4 (synthetic rolls cover about 4 squares)
Worked example
A 40 × 30 ft footprint = 1,200 sq ft. A 6/12 pitch has a factor of 1.118 → 1,342 sq ft of roof. With 10% waste that's 14.8 squares → 45 bundles and 4 rolls of underlayment.
Questions people ask
One square is 100 square feet of roof surface.
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Last updated September 28, 2026. These results are friendly estimates to help you plan — always double-check before buying or making big decisions.