Roof Shingle Calculator
Enter your roof's length, width and steepness and see how much material you need - roof area, squares, shingle bundles, underlayment, starter and ridge-cap, nails and a cost estimate, all updated live as you type. Everything runs in your browser, nothing uploaded.
Roof Area & Squares
Materials to Order
Estimated Cost
Material only. Excludes labour, flashing, vents, fasteners for ridge cap, and tax.
Learn more: estimating roof shingles
From footprint and pitch to roof area
The area a roof covers on the ground (its footprint) is smaller than the actual sloped surface you have to shingle. To convert, multiply the footprint by the pitch slope factor, which for a pitch written as rise over run is sqrt(1 + (rise/run)^2). A 6/12 pitch gives sqrt(1 + 0.5^2) = sqrt(1.25) = 1.1180, and the matching roof angle is arctan(6/12) = 26.6 degrees. So a 40 by 30 ft footprint (1,200 sq ft) becomes 1,200 x 1.1180 = 1,342 sq ft of roof, which is 13.42 roofing squares (one square = 100 sq ft).
Bundles, waste, underlayment and ridge cap
Architectural shingles are usually three bundles per square. Add a waste factor before ordering: about 10 percent for a clean gable, 15 to 20 percent for valleys, hips and dormers where diagonal cuts waste more material. From the example above, 13.42 squares plus 10 percent is 14.76 squares, so you need ceil(14.76 x 3) = 45 bundles. Underlayment is ordered by coverage - a synthetic roll covers about 10 squares, #15 felt about 4, #30 felt about 2. Ridge cap is measured in linear feet; a simple gable's ridge equals the building length, and one cap bundle covers roughly 20 linear feet.
Nails and what the estimate leaves out
Field nailing is estimated at four nails per shingle as standard, or six in high-wind zones and on steep slopes, with roughly 64 shingles per square. The totals here cover shingles, underlayment, drip edge and ridge cap only. They do not include flashing, valley metal, vents, pipe boots, labour or tax, and they assume a single rectangular gable. For hip, gambrel or multi-section roofs, add hip lengths in the extra ridge field and break complex shapes into rectangles.
FAQ
How do I turn a roof footprint into roof area?
Multiply the footprint area by the pitch slope factor. The slope factor for a pitch given as rise over run is sqrt(1 + (rise/run)^2). A 40 by 30 ft footprint is 1,200 sq ft; at a 6/12 pitch the factor is 1.1180, so the sloped roof area is 1,200 x 1.1180 = 1,342 sq ft, or 13.42 squares.
How many bundles of shingles are in a square?
Most architectural (laminate) shingles come three bundles to a square, where one square covers 100 sq ft of roof. Some heavier or premium shingles use four or five bundles per square, so check the wrapper. This calculator lets you set the bundles-per-square value and always rounds up to whole bundles.
How much waste should I add for shingles?
A simple gable roof with few cuts usually needs about 10 percent extra for trimming and starter. A roof with several valleys, hips or dormers runs closer to 15 to 20 percent because of the diagonal cuts. The calculator offers simple, moderate and cut-up presets and accepts any custom percentage.