Roofing Calculator
Estimate roofing material from the building footprint and roof pitch (actual roof area, roofing squares, and shingle bundles) with a waste allowance. Calculates in your browser.
Shingle bundles
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Show the math
The pitch multiplier scales the footprint up to the true sloped area:
pitch multiplier = √(rise² + 12²) ÷ 12
squares = footprint × multiplier × (1 + waste%) ÷ 100
A roofing square is 100 sq ft. Bundles per square depend on the shingle, so use the coverage on the wrapper (3 is only a starting value). Add waste for cuts, more for complex roofs with many hips and valleys. All math runs locally in your browser.
What this does
A roofing calculator estimates material from the footprint and roof pitch (actual roof area, roofing squares, and shingle bundles) with a waste allowance.
How to use it
- Enter the building footprint.
- Enter the roof pitch.
- Add a waste allowance.
- Read the squares and bundles.
How it works
The pitch multiplier scales the footprint up to the true sloped area. A square is 100 sq ft; bundles per square depend on the shingle, so use the coverage on the wrapper (the tool starts at 3).
pitch multiplier = √(rise² + 12²) ÷ 12
Understanding your result
The pitch multiplier is what turns your flat footprint into the true sloped area you actually cover, which is why a steep roof needs far more material than its floor plan suggests. Add the waste allowance for hips, valleys, and starter courses, and order a little extra, since matching a shingle color later across weathered and new bundles is difficult.
Example
A 1,500 sq ft footprint at 6/12 pitch is about 16.8 squares before waste, or 18.4 squares with the default 10% waste.
Last updated .
Frequently asked questions
What is a roofing square?
A square is 100 square feet of roof surface. Shingles are estimated by the square; how many bundles make a square depends on the product, so check the coverage printed on the bundle.
How does pitch change the area?
A sloped roof has more surface than its footprint. The pitch multiplier √(rise² + 12²) ÷ 12 scales the footprint up to the true area.
How much waste should I add?
About 10% covers cuts, ridges, and starter courses; complex roofs with many hips and valleys need more.
Do you store my numbers?
No. Everything is calculated locally in your browser.
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