What this estimate excludes
Complex roofs need a measured roof takeoff. Valleys, hips, dormers, overhangs, underlayment, starter strips, ridge caps and flashing are separate material decisions.
Example
A 40 ft by 24 ft plan area is 960 square feet before pitch. A 6/12 pitch increases roof surface area by the pitch factor, then waste is added before converting to roofing squares.
Common mistakes
Do not use flat plan area as final roof area on a pitched roof. Also remember that bundles per square vary by shingle type.
Limitations
This calculator is a material estimate only. It does not inspect roof structure, code requirements, ventilation, flashing, safety or installer waste practices.
Last reviewed: 2026-05-17