A roof is priced in squares — 100 square feet of roof surface each. Your roof's surface is bigger than its ground footprint because of pitch: a 6/12 roof has about 12% more surface than the same house under a flat roof. The calculator multiplies footprint by the pitch factor, adds 10% for waste and complexity, then prices those billable squares at the published installed rate for your material and state (tear-off of one layer included; extra layers added per square).
Pitch multipliers
| Pitch | Surface multiplier |
|---|---|
| 2/12 | × 1.014 |
| 3/12 | × 1.031 |
| 4/12 | × 1.054 |
| 5/12 | × 1.083 |
| 6/12 | × 1.118 |
| 7/12 | × 1.158 |
| 8/12 | × 1.202 |
| 9/12 | × 1.25 |
| 10/12 | × 1.302 |
| 11/12 | × 1.357 |
| 12/12 | × 1.414 |
Prefer the satellite version? The estimator measures your actual roof — every section and slope — from imagery.