Roofing Calculator
Estimate roof area in squares and shingle bundles from the footprint and the pitch. One square is 100 square feet.
Use it when you know the building footprint and the pitch and need squares and shingle bundles.
How this calculator works · Roofing estimate from your measurements
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How we calculated this
A roofing square is 100 square feet. The footprint is adjusted by the pitch multiplier, the square root of rise squared plus 12 squared, divided by 12. Waste is added, then bundles assume three bundles per square and round up.
What does this mean?
This roof is about 14.76 squares, or 45 bundles, including waste. Hips, valleys, and starter courses can need more.
Your assumptions
Edit assumptions- Footprint
- 40.0 × 30.0 ft
- Pitch
- 6.0 / 12
- Waste
- 10%
This calculator provides an estimate for planning. Material yield, waste, prices, and local requirements may vary.
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How the estimate is calculated
The footprint is adjusted by a pitch multiplier so a steeper roof has more surface.
Waste is added. Bundles assume three bundles per square and round up.
Roof area
Pitch multiplier = square root(rise² + 12²) ÷ 12. Squares = footprint area × multiplier × (1 + waste) ÷ 100.
Example
- Measure the building footprint, not the sloped surface, unless you already know the roof area. If you know the roof area, set pitch to 0 and enter that area as length times width.
- Use the pitch in rise per 12. A 6/12 roof uses 6.
- Start with 10% waste and raise it for a complicated roof.
With the numbers filled in on this page, the estimate is 14.76 squares.
What changes the result
Pitch
A steeper roof has more surface than the footprint. A flat roof uses a multiplier of 1.
Waste
Hips, valleys, and starter courses are why waste is more than zero.
Bundles
Three bundles per square fits common asphalt shingles. Some products pack differently.
Questions
What is a roofing square?
100 square feet of roof surface.
How do I enter pitch?
Enter the rise only. A 6/12 pitch is 6.
Does this include underlayment and ridge cap?
The area can be used for underlayment. Ridge cap and starter are not broken out as separate products.