roof pitch factor 20

https://alpha-wiki.win/index.php/How_to_Measure_a_Roof_Like_a_Pro:_A_Practical_Guide_for_Accurate_Estimates

Figuring out the roof pitch factor is a key step in many roofing projects. When you see a roof's slope expressed as a ratio, like 6:12, the pitch factor is the conversion tool that adjusts your measurements for that slope. Instead of measuring along a flat plane, the factor accounts for the extra length on the angled surface. So if you're calculating material quantities, the pitch factor ensures you're ordering enough to cover the full, sloped area, not just the footprint of the house. It's a p…