Roof Area Calculator
Calculate the approximate area of a simple roof from projected area and pitch.
Area of a simple roof
Enter projected length and width or a known projected area. That area is adjusted using the cosine of the angle, and pitch may be entered as percent or degrees; those values are not equivalent.
Sloped area = projected area ÷ cos(angle)
Geometric scope
This works for simple single- or dual-plane roofs when projected area is known. It does not model valleys, hips, mansards, irregular overhangs, or structure.
Frequently asked questions
Is 10% pitch the same as 10°?
No. A 10% grade is approximately 5.71°.
Does area increase with pitch?
Yes. The inclined surface is larger than its horizontal projection.
Does it calculate roofing materials?
It reports area; laps and product coverage must come from the selected material.
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