Measurement tool
Roof Square Calculator
Roofers buy, bid and talk in squares, not square feet. Enter your roof area to convert it, with and without a waste allowance.
A roofing square is 100 square feet of roof surface. Divide your roof area in square feet by 100 to get squares. A 2,000 sq ft roof is 20 squares, and each square takes 3 bundles of asphalt shingles, so 60 bundles before waste.
Convert to roofing squares
Enter actual roof surface area. If you only have the footprint, use the square footage calculator first.
Roofing squares
20.0
at 100 sq ft per square
Why roofers use squares
A square is 100 square feet of roof surface. The unit exists because roofing materials are packaged to it: three bundles of asphalt shingles cover one square, and a roll of underlayment covers three to four. Quoting in squares means the material order and the labor bid use the same denominator, which is why every contractor estimate you receive will be expressed that way.
It also makes labor legible. A crew installs roughly one square per hour per roofer on a straightforward tear-off and replace, so a 20-square roof is about 60 man-hours including removal and underlayment.
How much waste to add
Waste covers cuts, starter courses, ridge caps and mistakes. A simple gable roof with two planes wastes little, so 10% is enough. Hip roofs cut every course into the hips and need about 15%. Roofs with multiple valleys, dormers or steep pitches run 15% to 20%.
Waste is not optional padding. Running short mid-job means a second delivery, a stalled crew, and possibly a shingle lot that does not colour-match. Ordering an extra bundle is far cheaper than either.