What Is the Hip Roof Shingle Calculator?
A hip roof slopes downward on all four sides, so its total surface area is larger than the building footprint. This calculator estimates the sloped roof area, the number of roofing squares (one square = 100 sq ft), and the number of asphalt shingle bundles you need to buy. Because shingles are sold by the bundle (typically 3 bundles per square), planning by bundle prevents both shortages and costly over-ordering.
How to Use It
Enter the building footprint length and width in feet, the roof pitch as rise per 12 inches of run (e.g. a 6/12 roof rises 6 inches per foot), and a waste factor percentage. A 10% waste factor is common; complex hip roofs with many hips and valleys may need 12-15%.
The Formula Explained
The flat footprint is converted to true sloped area using the pitch multiplier, where \(L\) = length, \(W\) = width, and \(P\) = rise per 12:
$$A = L \times W \times \frac{\sqrt{P^2 + 144}}{12}$$Adding waste \(w\) (as a decimal) and converting to bundles at 3 per square:
$$B = \left\lceil \frac{A (1 + w)}{100} \times 3 \right\rceil$$
Worked Example
For a 40 ft × 30 ft building with a 6/12 pitch and 10% waste:
$$A = 40 \times 30 \times \frac{\sqrt{6^2 + 144}}{12} = 1200 \times 1.1180 = 1341.64\,\text{sq ft}$$With waste: \(1341.64 \times 1.10 = 1475.81\) sq ft = \(14.76\) squares.
$$B = \lceil 14.76 \times 3 \rceil = \lceil 44.27 \rceil = 45\,\text{bundles}$$FAQ
Does the footprint method work for hip roofs? Yes. Whether a roof is gable or hip, the total sloped area over a rectangular footprint is the same — the pitch multiplier accounts for the slope on all sides.
How many shingles in a bundle? Standard 3-tab and architectural shingles come 3 bundles per 100 sq ft square; heavier shingles may need 4 or 5 bundles per square.
Should I add extra for hips and ridges? Hip and ridge caps are usually bought separately. Increase the waste factor to 12-15% on roofs with many hips, valleys, and dormers.
