The math behind the numbers
Roof surface is the footprint multiplied by a pitch factor of √(1 + (rise ÷ 12)²). A 4/12 roof is about 5.4% larger than its footprint, a 6/12 roof about 11.8% larger, and a 12/12 roof about 41.4% larger. One square is 100 square feet.
Comparing with the carrier’s estimate
- Find total roof squares and the waste percentage in the roofing section.
- Differences of more than 5–10% deserve a second look.
- Look for steep and high-roof charges on steeper or two-story sections.
- Check that starter, ridge cap, drip edge, ice and water shield and valley metal are listed. Ice and water shield at the eaves is often required by local code in snowy parts of Wyoming.
When a footprint isn’t enough
Cut-up roofs with several pitches, dormers and valleys need to be measured plane by plane. Treat this as a sanity check, and rely on a field measurement or aerial report for the real number.
Questions about this calculator
How many squares does a typical house have?
A single-story Wyoming ranch might have 20 to 30 squares; a larger two-story with a complex roof can have 40 or more.
Why does waste vary?
Hips, valleys and dormers require more cutting, so more material ends up as scrap. Simple gables waste the least.