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Calculator 06 / Roofing

Roofing Calculator

Estimate roofing squares, shingle bundles, and underlayment rolls from your roof footprint and pitch.

Measure the building footprint to the drip edge (including overhang).

A 6/12 pitch rises 6" for every 12" of run. Use 0 for flat/low-slope.

10% for simple gable roofs; 15%+ for hips, valleys, and cut-ups.

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How this calculator works

Footprint area (ft²) = Length × Width Pitch multiplier = √(Rise² + 12²) ÷ 12 Roof area (ft²) = Footprint area × Pitch multiplier Squares = (Roof area × (1 + Waste %)) ÷ 100 Bundles = ceil(Squares × Bundles per square) Underlayment rolls = ceil(Squares ÷ 4) (standard 4-square roll)

A "square" is roofing shorthand for 100 square feet of roof surface. The pitch multiplier converts your flat footprint measurement into actual sloped roof area — steeper roofs have more surface area to cover than their footprint suggests.

Why does pitch matter if the footprint is the same?

A sloped surface covers more area than its flat footprint. At a 6/12 pitch the roof surface is about 12% larger than the footprint; at 12/12 it's about 41% larger.

How much extra should I order for hips and valleys?

Complex rooflines with multiple hips, valleys, and dormers typically need 15–20% waste versus 10% for a simple gable roof, due to extra cutting.

Estimates only. Confirm final material counts with your roofing supplier and manufacturer's coverage specs, especially for ridge cap and starter strip shingles, which are ordered separately.