Roof pitch chart
Every common pitch as an angle, a slope multiplier and a framing-square figure, with whether asphalt shingles are allowed on it. The multiplier is what turns a footprint into a roof area.
| Pitch | Angle | Slope multiplier | Common rafter per foot of run | Asphalt shingles |
|---|---|---|---|---|
| 1:12 | 4.8° | 1.0035 | 12.0416" | Not allowed |
| 2:12 | 9.5° | 1.0138 | 12.1655" | Doubled underlayment |
| 3:12 | 14.0° | 1.0308 | 12.3693" | Doubled underlayment |
| 4:12 | 18.4° | 1.0541 | 12.6491" | Standard |
| 5:12 | 22.6° | 1.0833 | 13.0000" | Standard |
| 6:12 | 26.6° | 1.1180 | 13.4164" | Standard |
| 7:12 | 30.3° | 1.1577 | 13.8924" | Standard |
| 8:12 | 33.7° | 1.2019 | 14.4222" | Standard |
| 9:12 | 36.9° | 1.2500 | 15.0000" | Standard |
| 10:12 | 39.8° | 1.3017 | 15.6205" | Standard |
| 12:12 | 45.0° | 1.4142 | 16.9706" | Standard |
Reading it
- The slope multiplier is the number to multiply a plan area by to get the sloped area of the roof over it. It is also hypot(12, rise) ÷ 12, which is why it and the per-foot rafter figure are the same number twelve times apart.
- IRC R905.2.2 sets 2 in 12 as the minimum rise for asphalt shingles, with doubled underlayment required under 4 in 12. 2021 IRC, defaults rather than law — the building department decides.
- Anything over about 6/12 stops being comfortable to walk and starts needing staging. That is a working judgement, not a code figure.
For the case this table does not cover
- Rafters
Common, hip and jack rafters for any pitch, with the birdsmouth laid out and the cut angles alongside.
- Roofing calculator
Squares, bundles, starter strip, ridge cap and underlayment from a building footprint and a pitch.