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Construction Calculators

Roofing Calculator

Calculate the number of roofing "squares" needed to cover a roof based on its footprint and pitch.

ft
ft
Roughly 1.0 for flat roofs, 1.15 for a 6:12 pitch, 1.30 for a 9:12 pitch, 1.42 for a 12:12 pitch.
%
Roof surface area —
Roofing squares needed —
Ad Space — 300×250

About the Roofing Calculator

Roofing materials are sold and installed by the "square," a unit equal to 100 sq ft of roof surface. This calculator converts your building's footprint into actual roof surface area by applying a pitch multiplier that accounts for the roof's slope, then converts that to squares.

Formula: Roof Area = Building Footprint × Pitch Multiplier × (1 + Waste %); Squares Needed = Roof Area ÷ 100

Steeper roofs have more surface area than their footprint suggests — a 6:12 pitch adds about 15%, while a 12:12 pitch adds about 42%. Always include a 10-15% waste allowance for hips, valleys and ridge cuts.

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