Roofing Squares Calculator
Convert a roof area into roofing squares and shingle bundles, adjusted for pitch and waste, with an optional material cost.
How it works
roof area = footprint × pitch multiplier · squares = area × (1 + waste%) ÷ 100 · bundles = squares × 3 (rounded up)
A "square" is roofing shorthand for 100 square feet of roof surface, the unit shingles and underlayment are sold and priced by. Your ground footprint has to be scaled up by the pitch multiplier — a 6/12 roof is about 1.118× longer along the slope than across the ground — and then padded for the shingles wasted on hips, valleys and starter cuts. Most architectural and three-tab shingles run three bundles to a square, so bundles are squares times three, rounded up to whole bundles.
Worked example
A 40 × 30 ft footprint is 1,200 sq ft. At 6/12 pitch the multiplier is 1.118, giving 1,342 sq ft of roof. Add 10% waste → 1,476 sq ft, which is 14.76 squares, or 45 bundles of shingles.
Frequently asked questions
What exactly is a roofing square?
One square equals 100 square feet of finished roof surface. Shingles, underlayment and labor are all quoted per square, so converting your area into squares is the first step in pricing any roof.
How much waste should I allow?
Ten percent is typical for a simple gable roof. Complicated roofs with many hips, valleys and dormers can waste 15% or more, because every valley and rake needs shingles cut on an angle and discarded.
How many bundles are in a square?
Most three-tab and architectural shingles are packaged three bundles per square. Heavier designer or premium shingles can take four or five bundles per square, so check the wrapper before you order.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.