How do I calculate roof area?

Multiply the flat footprint by the slope factor for your pitch — for example 1.118 for a 6/12 roof. The actual roof surface is larger than the footprint.

Pitch is the rise in inches per 12 inches of horizontal run. A 6/12 roof rises 6 inches per foot. Steeper pitches have a larger slope factor and more area.

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Roof Area Calculator

Actual roof area from footprint and pitch.

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Roof footprint (sq ft)Roof pitch

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How to use this calculator

Enter the roof's flat footprint area.
Choose the roof pitch.
See the actual sloped roof area and squares.

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Frequently asked questions

How do I calculate roof area?: Multiply the flat footprint by the slope factor for your pitch — for example 1.118 for a 6/12 roof. The actual roof surface is larger than the footprint.
What is roof pitch?: Pitch is the rise in inches per 12 inches of horizontal run. A 6/12 roof rises 6 inches per foot. Steeper pitches have a larger slope factor and more area.