Roofing Calculator
Roofers measure in squares — 100 square feet each — adjusted up for the roof slope. Enter your ground footprint and pitch to get squares, shingle bundles, and cost.
How to measure a roof
Start with the building footprint — length × width — then adjust for slope. A flat-looking footprint understates a pitched roof, so the calculator applies a slope multiplier based on your pitch (the rise in inches per 12 inches of run).
Squares and bundles
Roofing is sold and quoted by the square (100 sq ft), with about 3 bundles of shingles per square. Add 10% for cut waste plus extra for hips, valleys, and ridge caps on a complex roof.
Cost
Multiply bundles by price for the shingle material only — underlayment, flashing, nails, and labor are separate. For dimensions of a complex roof plane, the square footage calculator helps break it into sections.
Frequently asked
What is a roofing square?
A square is 100 square feet of roof surface. Shingles, underlayment, and labor are all quoted per square. A 1,340 sq ft roof is 13.4 squares.
How many bundles of shingles per square?
Most architectural shingles come 3 bundles to the square. Heavier designer shingles may take 4 or more. Always add 10% for waste, hips, and ridges.
How does roof pitch change the amount?
A steeper roof has more surface than its flat footprint. The calculator multiplies the footprint by a slope factor from your pitch — a 6/12 roof is about 12% larger than the ground area.