Reference
Roof pitch chart
Pitch is rise per 12 inches of run. The slope factor turns flat footprint area into sloped roof area. Pick a pitch for its own page with area tables and code notes.
| Pitch | Angle | Grade | Slope factor | Extra area | Asphalt shingles (IRC) |
|---|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.0035 | +0.3% | Not allowed |
| 2/12 | 9.5° | 16.7% | 1.0138 | +1.4% | Allowed, double underlayment |
| 3/12 | 14° | 25% | 1.0308 | +3.1% | Allowed, double underlayment |
| 4/12 | 18.4° | 33.3% | 1.0541 | +5.4% | Allowed |
| 5/12 | 22.6° | 41.7% | 1.0833 | +8.3% | Allowed |
| 6/12 | 26.6° | 50% | 1.1180 | +11.8% | Allowed |
| 7/12 | 30.3° | 58.3% | 1.1577 | +15.8% | Allowed |
| 8/12 | 33.7° | 66.7% | 1.2019 | +20.2% | Allowed |
| 9/12 | 36.9° | 75% | 1.2500 | +25% | Allowed |
| 10/12 | 39.8° | 83.3% | 1.3017 | +30.2% | Allowed |
| 11/12 | 42.5° | 91.7% | 1.3566 | +35.7% | Allowed |
| 12/12 | 45° | 100% | 1.4142 | +41.4% | Allowed |
| 13/12 | 47.3° | 108.3% | 1.4743 | +47.4% | Allowed |
| 14/12 | 49.4° | 116.7% | 1.5366 | +53.7% | Allowed |
| 15/12 | 51.3° | 125% | 1.6008 | +60.1% | Allowed |
| 16/12 | 53.1° | 133.3% | 1.6667 | +66.7% | Allowed |
| 17/12 | 54.8° | 141.7% | 1.7341 | +73.4% | Allowed |
| 18/12 | 56.3° | 150% | 1.8028 | +80.3% | Allowed |
Frequently asked questions
How do I convert roof pitch to degrees?
Take the arctangent of rise divided by 12. A 6/12 pitch is atan(0.5), about 26.6 degrees.
What is a roof pitch multiplier?
It is the slope factor, √(1 + (rise ÷ 12)²). Multiply the flat footprint area by it to get the roof surface area.
What is the most common roof pitch?
Many houses fall between 4/12 and 8/12, but the only reliable answer for your house is a measurement.