Roofing Calculator
Measure the footprint of the house, not the roof itself. Pick the pitch and this works out the real sloped area, the squares and the bundles.
How the math works
Roof area = the footprint x the pitch multiplier. A 6/12 pitch multiplies by 1.118, because the slope is the hypotenuse of a 6 and 12 triangle. Squares = area divided by 100. One square is 100 square feet and takes 3 bundles of architectural shingle.
Common questions
- How many bundles of shingles do I need per square?
- Three for a standard architectural shingle. Some heavier designer shingles take four or five, so check the bundle, because ordering by square and assuming three is how people end up a pallet short.
- How do I work out roof area without climbing on the roof?
- Measure the footprint on the ground, including the overhang, then multiply by the pitch factor. A 6/12 roof is 1.118 times its footprint, an 8/12 is 1.202.
- What is a roofing square?
- One hundred square feet of roof. Everything in roofing is priced and ordered by the square, not the square foot, which is why a quote sounds so different from a materials list.
- How much waste should I allow?
- Ten percent on a simple gable, fifteen with hips, valleys or dormers. Valleys waste the most because every course gets a diagonal cut.
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