Roofing Calculator

Turn a building footprint and pitch into roof area, squares and bundles.

Building length

Building width

Pitch rise (in 12) (/12)

Waste (%)

Roof area 1,475.8

Roofing squares (sq) 14.758

Shingle bundles (bundles) 45

Formula: roof area = footprint × √(rise² + 144) ÷ 12 × (1 + waste)

Step-by-step with your numbers:

1. Values used:

2. Building length = 40

3. Building width = 30

4. Pitch rise (in 12) = 6 /12

5. Waste = 10 %

7. Roof area = 1,475.8

8. Roofing squares = 14.758sq

9. Shingle bundles = 45bundles

Did we solve your problem today?

Estimate the actual roof surface area from the building footprint and pitch, then convert it to roofing 'squares' and shingle bundles.

The math behind it

A pitched roof is larger than its flat footprint. Multiply the footprint by the slope factor = √(rise² + 12²) ÷ 12.

1 roofing square = 100 ft². Asphalt shingles come ~3 bundles per square.

40×30 ft footprint (1,200 ft²) at 6/12 (slope 1.118) + 10% waste → ~1,476 ft² ≈ 15 squares ≈ 45 bundles.

What is a roofing square?

A unit equal to 100 square feet of roof surface — the standard way roofers quote materials.