How this estimate works
The calculator applies: ceil(length x width x pitchFactor x (1 + waste/100) / coverage). Keep measurements in one unit system and round up when suppliers sell whole units.
Limitations
Ridges, hips, valleys, underlayment, starter strips, and multiple roof planes are separate.
Source to check
Read the authoritative guidance for roofing material calculator
Frequently asked question
What is pitch factor? It converts horizontal footprint to sloped area; use a factor for each roof plane.