Roofing Calculator
Calculate roof area, roofing squares, and shingle bundles needed based on roof dimensions and pitch.
About the Roofing Calculator
Roof area is larger than the building's footprint because of the slope, and roofing material is bought in "squares" (100 sq ft units) and bundles — this calculator accounts for pitch and waste to estimate the material you actually need to order.
How It Works
The calculator multiplies the roof's footprint (length × width) by a pitch multiplier that approximates how much the slope increases the actual surface area compared to a flat measurement, then adds your waste allowance. It converts that final area into roofing squares (each covering 100 sq ft) and estimates shingle bundles at roughly 3 bundles per square, the typical bundling standard.
Roof Area = Footprint × Pitch Factor × (1 + Waste%); Squares = Area / 100; Bundles ≈ Squares × 3.
Example
Scenario: A 40ft × 30ft footprint with a medium pitch and 10% waste allowance.
Result: About 1,518 sq ft of actual roof area, roughly 15.2 roofing squares, and approximately 46 bundles of shingles.
Assumptions & Limitations
- Pitch factors are approximations — flat roofs use close to the footprint area, while steeper pitches increase the multiplier to reflect the additional surface area created by the slope.
- Assumes standard 3-bundle-per-square shingle packaging, which is typical but can vary slightly by manufacturer.
- Complex roofs with multiple planes, dormers, or valleys need a more detailed measurement than a simple footprint-based estimate — consult a roofing professional for irregular roof shapes.
- Actual pitch varies continuously; the preset categories here are approximations of common pitch ranges.