Roofing Calculator
Squares, shingle bundles, and underlayment from your footprint and pitch.
Your estimate
Estimates only. Renovate Cafe's calculators are a planning aid, not professional advice — double-check your inputs, confirm coverage on the product you buy, and verify quantities and local code for structural, electrical, or permitted work. Disclaimer.
Enter the footprint your roof covers and its pitch. Renovate Cafe applies the slope factor, adds waste, and returns the roof area in squares, the shingle bundles, the underlayment rolls, and the cost.
Footprint, pitch, and squares
Roofers measure in squares — one square equals 100 square feet of roof surface. The tricky part is that a sloped roof has more surface than the ground it covers. So you measure the footprint (length × width as seen from above) and multiply by a slope factor that depends on the pitch.
A 6/12 roof, for example, has a slope factor of about 1.12, so it has 12% more surface than its footprint. The calculator stores the factor for every common pitch and does this for you. Divide the resulting roof area by 100 and you have your squares.
Bundles, waste, and underlayment
Standard architectural shingles run three bundles per square; heavier designer shingles run four. On top of that you add a waste factor — 10% for a simple gable roof, 15% when there are hips and valleys to cut into, because every valley and rake edge means trimmed, discarded shingle.
You'll also need underlayment beneath the shingles; one roll of synthetic underlayment covers roughly 400 square feet, and the calculator rounds your rolls up. Order starter strip and ridge cap separately — they're sold by the linear foot, not the square. And if your roof is steep (8/12 and up) or two stories, price the job with a contractor; this is a calculator for materials, not a safety plan.
Frequently asked questions
How many bundles of shingles per square?
How do I measure roof pitch?
How much extra roofing should I buy for waste?
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