Roof Area Calculator
Calculate the actual surface area of a pitched roof.
How It Works
Footprint = (Length + 2×Overhang) × (Width + 2×Overhang). Surface = Footprint ÷ cos(atan(Pitch ÷ 12)).
Example
A 40 ft × 30 ft building at 4/12 pitch with 1 ft overhang: footprint = 42 × 32 = 1,344 sq ft, surface ≈ 1,417 sq ft.
Frequently Asked Questions
What is the overhang input?
The distance the roof extends past the walls. It adds to both length and width before the area is computed.
Why is surface area larger than footprint?
The roof is sloped, so it is always larger than the flat footprint it covers. Steeper pitches increase the difference.
Should I use this or the footprint for materials?
Always order materials based on the actual surface area, not the footprint.