What a 9/12 pitch means
The roof goes up 9 inches for every 12 inches it runs level. That works out to an angle of 36.87 degrees, a slope of 75.0 percent, and a pitch multiplier of 1.250. It is 3.2 degrees steeper than an 8/12 roof.
A 9/12 roof is in the conventional range, where most houses fall. It sheds water well and takes any common roofing. Over the same house, it has 25.0 percent more surface than a flat roof.
Rafter lengths at 9/12
These are measured from the ridge to the outside of the wall on a simple gable roof, before any overhang or ridge board is taken into account. For an exact length, use the rafter length calculator.
| Building width | Rafter length | Rise at ridge | Run |
|---|---|---|---|
| 12 ft | 7' 6" | 4' 6" | 6 ft |
| 16 ft | 10' 0" | 6' 0" | 8 ft |
| 20 ft | 12' 6" | 7' 6" | 10 ft |
| 24 ft | 15' 0" | 9' 0" | 12 ft |
| 28 ft | 17' 6" | 10' 6" | 14 ft |
| 32 ft | 20' 0" | 12' 0" | 16 ft |
| 36 ft | 22' 6" | 13' 6" | 18 ft |
| 40 ft | 25' 0" | 15' 0" | 20 ft |
Roof area at 9/12
Multiply the flat area the roof covers, overhangs included, by 1.250. One roofing square is 100 square feet.
| Area covered | Roof area | Squares |
|---|---|---|
| 1,000 sq ft | 1,250 sq ft | 12.5 |
| 1,500 sq ft | 1,875 sq ft | 18.8 |
| 2,000 sq ft | 2,500 sq ft | 25.0 |
| 2,500 sq ft | 3,125 sq ft | 31.3 |
| 3,000 sq ft | 3,750 sq ft | 37.5 |
Roofing that works at 9/12
The International Residential Code sets a lowest pitch for each kind of roofing. Here is how a 9/12 roof compares. Your local code and the maker instructions can be stricter.
| Roofing | Lowest pitch allowed | On a 9/12 roof |
|---|---|---|
| Asphalt shingles | 2 in 12 | Yes |
| Clay or concrete tile | 2 1/2 in 12 | Yes |
| Wood shingles or shakes | 3 in 12 | Yes |
| Metal roof shingles | 3 in 12 | Yes |
| Slate | 4 in 12 | Yes |
| Roll roofing, mineral surfaced | 1 in 12 | Yes |
| Standing seam metal | 1/4 in 12 | Yes |
| Membrane or built-up roofing | 1/4 in 12 | Yes |
| Metal panels with lapped seams | 3 in 12 | Yes |
Working on a 9/12 roof
As a rule of thumb, footing gets poor at 9/12. Roof jacks or a harness are normal at this pitch. Any roof is dangerous when wet or frosty. In the US, OSHA requires fall protection for workers doing residential construction 6 feet or more above a lower level.
Nearby pitches
Compare with the 8/12 roof pitch and 10/12 roof pitch, or see every pitch in the chart on the roof pitch calculator.
Common questions
What is a 9/12 roof pitch in degrees?
A 9/12 pitch is 36.87 degrees. The roof rises 9 inches for every 12 inches of level run, which is a 75.0 percent slope.
What is the pitch multiplier for a 9/12 roof?
It is 1.250. Multiply a level distance by 1.250 to get the distance along the roof, or multiply the area a roof covers by it to get the roof area.
How long is a rafter on a 24 foot wide building at 9/12?
About 15' 0" from the ridge to the outside of the wall, before any overhang or ridge board deduction. The ridge sits 9' 0" above the top of the wall.
Can you put asphalt shingles on a 9/12 roof?
Yes. A 9/12 roof is above the 4 in 12 mark, so asphalt shingles go on with standard single underlayment.
Is a 9/12 roof walkable?
As a rule of thumb, footing gets poor at 9/12. Roof jacks or a harness are normal at this pitch. Any roof is dangerous when wet.
Sources
- International Residential Code 2021, Chapter 9: roof coverings (R905)
- OSHA 29 CFR 1926.501: fall protection in construction
Facts on this page were last checked against these sources in October 2026.