How do I calculate roof area from house footprint?

Multiply your home's footprint (length × width) by a pitch multiplier: 1.03 for a low slope, 1.12 for medium (5/12–7/12), 1.25 for steep (8/12–10/12), and 1.41 for very steep roofs.

Is roof area the same as house square footage?

No. Roof area is always larger because the roof is angled. A 2,000 sq ft footprint typically becomes 2,240–2,500 sq ft of roof surface once pitch is factored in.

Calculator

Roof Area Calculator

Roof area is the first number every roofer needs. This calculator converts your home's footprint and pitch into total roof surface — the figure that drives every material list and cost estimate.

Home length

Home width

Pitch

Footprint

2,000 sq ft

Roof area

2,240 sq ft

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Frequently asked

How do I calculate roof area from house footprint?: Multiply your home's footprint (length × width) by a pitch multiplier: 1.03 for a low slope, 1.12 for medium (5/12–7/12), 1.25 for steep (8/12–10/12), and 1.41 for very steep roofs.
Is roof area the same as house square footage?: No. Roof area is always larger because the roof is angled. A 2,000 sq ft footprint typically becomes 2,240–2,500 sq ft of roof surface once pitch is factored in.

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