The math
Roof surface is larger than the footprint underneath it. The pitch multiplier is √(1 + (rise ÷ 12)²). A 5/12 roof is about 8.3% larger than its footprint; a 12/12 roof is about 41.4% larger. Idaho’s deep eaves add area too, so include overhangs.
Checking the insurer’s estimate
- Find total squares and the waste percentage in the roofing section.
- Enter the carrier’s squares here to see the difference. Gaps over 5–10% deserve a closer look.
- Look for steep charges, often starting around 7/12, and high-roof charges for two-story sections.
- Check that ridge cap, starter, drip edge and ice-and-water shield appear as separate lines.
Limits
Roofs with several pitches, dormers and valleys need plane-by-plane measurement. Aerial reports or a field measurement will be more accurate. Use this as a sanity check.
Questions about the roof squares calculator
What is a roofing square?
One square is 100 square feet of roof surface. Many Idaho single-family homes fall somewhere between 20 and 45 squares.
Why does waste change by roof style?
Hips, valleys and dormers need more cutting, so more material is lost as scrap.