Free Roofing Squares calculator with clear step-by-step results.
A roofing square is 100 square feet, or 9.29 square metres, and is the unit roofing materials are quoted in across North America. Plan area is converted to sloped area using the rise-in-twelve pitch, then divided into squares and used to size underlayment and fixings.
Sloped area
Sloped = plan area x square root of (1 + (rise / 12)^2)
Squares
Squares = sloped area m2 / 9.2903
One roofing square is 100 square feet, and one square foot is 0.092903 square metres. The conversion is exact rather than rounded.
Less. Underlayment runs in long courses with modest laps, so ordering to the sloped area plus one roll is usually sufficient.