Roof Pitch Chart
Roof pitch is expressed as a ratio of rise to horizontal run — a 6/12 pitch rises 6 inches for every 12 inches of horizontal distance. Use this chart for estimating materials, calculating rafter lengths, and determining whether a roof qualifies as low-slope, conventional, or steep per IRC requirements.
The Complete Roof Pitch Chart
| Pitch | Angle | Slope Factor | Decimal Slope | Category |
|---|---|---|---|---|
| 1/12 | 4.76° | 1.003 | 0.083 | Low-slope |
| 1.5/12 | 7.13° | 1.008 | 0.125 | Low-slope |
| 2/12 | 9.46° | 1.014 | 0.167 | Low-slope |
| 2.5/12 | 11.77° | 1.021 | 0.208 | Low-slope |
| 3/12 | 14.04° | 1.031 | 0.250 | Low-slope |
| 3.5/12 | 16.26° | 1.042 | 0.292 | Conventional |
| 4/12 | 18.43° | 1.054 | 0.333 | Conventional |
| 4.5/12 | 20.56° | 1.068 | 0.375 | Conventional |
| 5/12 | 22.62° | 1.083 | 0.417 | Conventional |
| 5.5/12 | 24.62° | 1.100 | 0.458 | Conventional |
| 6/12 | 26.57° | 1.118 | 0.500 | Conventional |
| 7/12 | 30.26° | 1.158 | 0.583 | Conventional |
| 8/12 | 33.69° | 1.202 | 0.667 | Conventional |
| 9/12 | 36.87° | 1.250 | 0.750 | Conventional |
| 10/12 | 39.81° | 1.302 | 0.833 | Steep |
| 11/12 | 42.51° | 1.357 | 0.917 | Steep |
| 12/12 | 45.00° | 1.414 | 1.000 | Steep |
| 14/12 | 49.40° | 1.537 | 1.167 | Steep |
| 16/12 | 53.13° | 1.667 | 1.333 | Steep |
| 18/12 | 56.31° | 1.803 | 1.500 | Steep |
| 20/12 | 59.04° | 1.944 | 1.667 | Steep |
| 24/12 | 63.43° | 2.236 | 2.000 | Steep |
How to Use the Slope Factor
The slope factor converts horizontal ground measurements into actual sloped roof surface area. If your house has a 40' × 30' footprint and a 6/12 pitch roof, the ground area is 1,200 square feet, and the roof surface area is 1,200 × 1.118 = 1,342 square feet. This is the number you use for calculating shingle quantities, underlayment, and decking.
The slope factor is calculated as √(rise² + run²) ÷ run. For a 6/12 pitch, that's √(6² + 12²) ÷ 12 = √180 ÷ 12 = 1.118.
Low-Slope vs Conventional vs Steep Roofs
Low-Slope (1/12 to 3/12)
Asphalt shingles are generally not allowed below 2/12 pitch without special double-layer underlayment, and most manufacturers void warranties below 4/12. Low-slope roofs typically use modified bitumen, TPO, EPDM, or built-up roofing systems. Water sheds slowly on low-slope roofs, so proper flashing and underlayment matters more than on steep roofs.
Conventional (4/12 to 9/12)
The most common residential range. Standard asphalt shingle installation, normal flashing details, and most architectural styles fall in this zone. 6/12 is the most common pitch on American homes. 8/12 is popular in snow country because it sheds snow well without being difficult to walk on.
Steep (10/12 and Above)
Requires special installation techniques — roof jacks, harnesses, and sometimes specialty fasteners because gravity works against the shingles. Architectural styles like Victorian, Tudor, and some Craftsman homes use 12/12 or steeper pitches. Above 21/12, many shingle manufacturers require hand-sealing each shingle because the self-sealing strips don't activate reliably on near-vertical surfaces.
Common Pitch Questions
What's the minimum pitch for asphalt shingles?
Most manufacturers specify 2/12 as the absolute minimum with double underlayment, and 4/12 as the minimum for standard installation with single-layer underlayment. Below 2/12, use membrane roofing systems.
What pitch is best for snow?
Pitches between 6/12 and 10/12 shed snow effectively while remaining walkable for maintenance. Very low pitches retain snow load (which stresses the structure); very steep pitches shed snow so dramatically that accumulation zones below can be dangerous. 8/12 is the sweet spot in most snow climates.
What pitch is best for solar panels?
Solar panels perform best when tilted roughly equal to the installation site's latitude. For most of the continental US (25° to 45° latitude), roof pitches between 5/12 and 9/12 (22° to 37°) are close enough to optimal that additional tilt mounts aren't needed.
Calculate Your Specific Roof
- Rafter Calculator — find rafter length, ridge height, and cutting angles for any pitch
- Roof Area Calculator — estimate shingle bundles, underlayment, and sheathing