12/12 Roof Pitch
A 12/12 roof (also written 12:12 or "12 on 12") rises 12 inches for every 12 inches of horizontal run: 45.00°, a 100.0% slope, and 41.4% more surface than its footprint.
| Measure | 12/12 value |
|---|---|
| Angle | 45.00° |
| Slope percent | 100.0% |
| Rise per foot of run | 12 in |
| Pitch multiplier (area factor) | 1.4142 |
| Hip/valley factor | 1.7321 |
| Common rafter length per foot of run | 17" |
| Plumb cut / seat cut | 45.0° / 45.0° |
Where you see a 12/12 roof
Typical uses: cape cods, Tudors, A-frame-style cabins and steep gables. A 12/12 roof rises one foot for every foot of run, so it sits at exactly 45 degrees. The multiplier is √2 (1.414): the roof has 41% more area than the footprint, and every rafter is 1.414 times its run. It is not walkable without equipment.
Roof area at 12/12
12/12 formulas
Worked examples
12/12 rafter lengths and ridge heights
| Building span | Run | Rafter (no overhang) | Ridge rise |
|---|---|---|---|
| 16 ft | 8 ft | 11' 3-3/4" | 8' 0" |
| 20 ft | 10 ft | 14' 1-11/16" | 10' 0" |
| 24 ft | 12 ft | 16' 11-5/8" | 12' 0" |
| 28 ft | 14 ft | 19' 9-9/16" | 14' 0" |
| 32 ft | 16 ft | 22' 7-1/2" | 16' 0" |
| 36 ft | 18 ft | 25' 5-1/2" | 18' 0" |
Roof area by footprint at 12/12
| Footprint (incl. overhang) | Roof area | Squares |
|---|---|---|
| 1,000 sq ft | 1,414 sq ft | 14.1 |
| 1,500 sq ft | 2,121 sq ft | 21.2 |
| 2,000 sq ft | 2,828 sq ft | 28.3 |
| 2,500 sq ft | 3,536 sq ft | 35.4 |
| 3,000 sq ft | 4,243 sq ft | 42.4 |
Materials and walkability
- Shingles: Yes. 4/12 and steeper takes a standard shingle installation.
- Walkable? Not without equipment. Plan on roof jacks, harnesses and anchors.
- OSHA class: Steep roof (OSHA): OSHA treats anything steeper than 4/12 as a steep roof for fall-protection rules.
Roofing materials allowed on a 12/12 roof
| Roof covering | Code minimum | OK at 12/12? |
|---|---|---|
| Standing-seam metal panels | 0.25/12 (IRC R905.10.2) | Yes |
| Built-up, modified bitumen, single-ply membrane (TPO, EPDM, PVC) | 0.25/12 (IRC R905.9, R905.11, R905.12) | Yes |
| Lapped metal panels with lap sealant | 0.5/12 (IRC R905.10.2) | Yes |
| Mineral-surfaced roll roofing | 1/12 (IRC R905.5.2) | Yes |
| Asphalt shingles | 2/12 (IRC R905.2.2) | Yes |
| Clay and concrete tile | 2.5/12 (IRC R905.3.2) | Yes |
| Metal roof shingles | 3/12 (IRC R905.4.2) | Yes |
| Lapped metal panels, no sealant (exposed-fastener) | 3/12 (IRC R905.10.2) | Yes |
| Wood shingles and shakes | 3/12 (IRC R905.7, R905.8) | Yes |
| Slate | 4/12 (IRC R905.6.2) | Yes |
Sources
- International Code Council, International Residential Code (2021 and 2024), Section R905 minimum slopes, as summarized in IRC 2024 Chapter 9 (UpCodes) and the MyBuildingPermit residential re-roof checklist. Local amendments and manufacturer instructions can be stricter.
- OSHA, 29 CFR 1926.500(b): a low-slope roof is 4 in 12 or less; a steep roof is greater than 4 in 12. 1926.501(b)(13) requires fall protection for residential construction work 6 ft or more above a lower level.
← 11/12 pitch · All pitches in degrees
Frequently asked questions
How many degrees is a 12/12 roof pitch?
A 12/12 roof pitch is 45.00 degrees.
What is the multiplier for a 12/12 pitch?
The pitch multiplier for 12/12 is 1.4142. Multiply the footprint area or horizontal run by it to get the sloped area or rafter length.
Can you put shingles on a 12/12 roof?
Yes. 4/12 and steeper takes a standard shingle installation.
Is a 12/12 roof walkable?
Not without equipment. Plan on roof jacks, harnesses and anchors.
Last reviewed 2026-10-21. Results are estimates for planning; confirm quantities with your supplier and requirements with your local building code and the manufacturer's instructions.