Squares, pitch, and why the roof is bigger than the house
<Assets TBC> Side view of a 6 in 12 roof with the extra length marked
Roofers measure in squares. One square is 100 square feet of roof, and most architectural shingles come three bundles to the square.
A sloped roof covers more area than the floor under it. A 6 in 12 roof rises 6 inches for every 12 across, so each foot of footprint becomes about 1.12 feet of roof. On a 12 in 12 roof it becomes about 1.41 feet. Measure the footprint and forget the pitch, and the order comes up short.
Pitch changes labour too, since steep roofs need more safety gear and go slower. RoofTools will read each plane's pitch from LiDAR so the material count and the labour use the same number. It is in development.