How to use
- Enter the horizontal plan size of the roof, length times width, not the sloped surface.
- Enter the pitch as rise and run. A 6 in 12 pitch is rise 6 and run 12.
- Confirm bundles per square on the package. Leave waste at 10 percent or change it for hips and valleys.
- Press Calculate. The hero is field bundles, rounded up. Buy starter and ridge cap separately.
How it's calculated
Slope factor = square root of (rise squared + run squared) ÷ run. Sloped area = plan area × slope factor.
Squares = sloped area × (1 + waste) ÷ 100. Bundles = squares × bundles per square, rounded up. The ClearQuip roof pitch page explains the same slope factor and stops at area. This page continues to bundles.
Worked example
A 20 by 30 foot plan is 600 square feet. A 6:12 pitch has a slope factor of about 1.118, so the sloped area is about 670.8 square feet before waste. At 10 percent waste that is about 7.38 squares. At 3 bundles per square the order is 23 bundles after rounding up from 22.14.
Assumptions
One rectangular plan and one pitch. Hips, valleys, and dormers need more waste than a simple gable. Starter strip and ridge cap are extra linear-foot products and are omitted on purpose.
FAQ
Is a square 100 square feet of floor?
No. For shingles, a square is 100 square feet of roof surface, after the slope factor.
Why isn't ridge cap in the count?
Ridge cap is sold by the linear foot of ridge, not by the field square. Measure the ridge and use that product's coverage.
What if the pitch is 0:12?
A flat roof has a slope factor of 1. Many asphalt shingles are not rated for a flat roof. The math still runs. The product choice is yours.
Does 3 bundles always make a square?
It is the usual field packaging. Architectural shingles sometimes differ. Read the bundle.