Use this roof area calculator to estimate sloped roof surface area from a horizontal footprint and roof pitch. Add a waste allowance to produce a planning quantity for materials.
How the Calculation Works
The calculator multiplies a horizontal roof footprint by the slope factor created by the entered rise. It then applies the waste allowance and converts the result to roofing squares, where one roofing square equals 100 square feet.
When This Estimate Works Best
This method works best for simple roofs when you already have a reasonable horizontal footprint estimate. Complex hips, valleys, dormers, additions, overhangs and multiple pitches should be measured section by section.
Use the Roof Pitch Calculator if you need the pitch first, or continue to the Roofing Squares Calculator.