The math behind it
Roof surface area equals footprint times a pitch multiplier of √(1 + (rise ÷ 12)²). At 4/12 the roof is about 5.4% larger than its footprint; at 8/12, about 20.2%; at 12/12, about 41.4%.
Checking the carrier’s roof section
- Compare total squares and the waste percentage.
- Differences above 5–10% deserve a closer look.
- Look for steep charges on 7/12 and steeper roofs and high-roof charges on two-story sections.
- Confirm ridge cap, starter, drip edge and ice-and-water shield are listed. Ice barrier along eaves is common on Utah roofs.
Limitations
Roofs with several pitches, dormers and valleys should be measured plane by plane. A field measurement or aerial report is always more accurate than a footprint estimate.
Questions about this calculator
What’s a roofing square?
100 square feet of roof surface. Many Wasatch Front homes have roughly 25 to 45 squares.
Why does waste vary?
Hips, valleys and dormers require more cutting, so more material is wasted.