The math
A roof’s surface is larger than its footprint because it slopes. The pitch multiplier is the square root of 1 + (rise ÷ 12)². Multiply the footprint, including overhangs, by that factor to get the surface area, then divide by 100 for squares. Waste covers cutting at hips, valleys and dormers.
Why it matters
A difference of a few squares, or a waste factor that’s too low for a cut-up roof, adds up quickly. Steep pitches usually also carry steep charges in estimating software, and two-story or three-story roofs may carry high charges.
This converter treats the roof as a single plane over the footprint. Complex roofs should be measured slope by slope.
Questions about this tool
What is a roofing square?
One square is 100 square feet of roof surface.
Why does my estimate show more squares than my footprint?
Pitch and waste both increase the quantity. A 12/12 roof has about 41% more surface than its footprint.
When do steep charges apply?
Estimating software commonly adds steep charges starting around 7/12 or 8/12, and more at higher pitches. Check how your estimate treats your pitch.