Free roofing tool

Roof area calculator

Turn your home footprint and roof pitch into actual roof area — the number that sets your price.

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Your roof is bigger than your home’s floor plan because it is sloped. Enter your footprint (ground-level square footage) and pitch to estimate your true roof area.

Estimated roof area
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An estimate from footprint and pitch. Overhangs and dormers add a little more.

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Why your roof is bigger than your floor plan

A sloped roof covers more surface than the flat footprint beneath it. The steeper the pitch, the bigger the multiplier. This calculator multiplies your footprint by the pitch factor to estimate roof area. To find your pitch, use the roof pitch calculator.

Cost ranges reflect 2026 U.S. installed prices (BLS producer/labor data, Remodeling Cost vs. Value, and manufacturer pricing). Your real price depends on your roof, region, and pro — see the full cost guide.

FAQ

Roof Area Calculator questions

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Multiply your home’s footprint (ground-level area the roof covers) by a pitch factor. A 6/12 roof multiplies by about 1.12; a steep 12/12 by 1.41. This tool does the math for you.
No. Your roof is sloped, so it covers more area than the flat footprint — and a two-story home’s footprint is far smaller than its total floor size. Always price by roof area.
A multiplier for how steep your roof is. It equals the length of the slope divided by the horizontal run — steeper roofs have bigger factors and more surface area.
Yes, a little. Eaves and overhangs add surface beyond the footprint. This estimate is close; a pro measures exactly.

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