Quantity reference
Roof Pitch Multipliers Reference Chart
Mathematical conversion from horizontal projected roof area to sloped plane area for uniform pitch. Extra roof planes, dormers and overhangs must be measured separately.
| Roof rise per 12 in | Area multiplier | Approx. slope angle |
|---|---|---|
| 2/12 | 1.0138 | 9.46° |
| 3/12 | 1.0308 | 14.04° |
| 4/12 | 1.0541 | 18.43° |
| 5/12 | 1.0833 | 22.62° |
| 6/12 | 1.1180 | 26.57° |
| 8/12 | 1.2019 | 33.69° |
| 10/12 | 1.3017 | 39.81° |
| 12/12 | 1.4142 | 45° |
Before using these quantities in a bid
- Multiply each plane’s horizontal area by the multiplier for its pitch.
- Pitch calculation is geometry only, not a complete roof takeoff.
- Roofing material waste is separate from slope area.
Reference values are nominal or mathematical planning aids unless otherwise stated. Confirm actual product data, approved drawings, applicable requirements, jobsite conditions, and supplier information. These pages contain no live price feed and do not replace professional judgment.
Turn your reference check into a better estimate
Use the related free calculator for one-off math, or explore the professional trade estimating workflow for plan-based quantities, materials and labor.