What roof pitch means
Pitch is how steep a roof is. Roofers write it as the rise in inches for every 12 inches of run. A 6:12 roof climbs 6 inches for each foot it runs in. Pitch matters for the material too. The International Residential Code, section R905.2.2, asks for a slope of at least 2:12 for asphalt shingles, and extra underlayment below 4:12. A flatter roof needs a low-slope or flat roof system.
To measure it, hold a level flat against the roof or a rafter, mark 12 inches along the level, and measure straight up from that mark to the roof. That number is the rise. You can also measure from inside the attic. Stay off a steep or wet roof.
Common roof pitches
The multiplier is the roof area over the footprint area. Multiply the footprint of the house, with the overhang, by it to get the roof area.
| Pitch | Angle | Multiplier |
|---|---|---|
| 2:12 | 9.5° | 1.014 |
| 3:12 | 14° | 1.031 |
| 4:12 | 18.4° | 1.054 |
| 5:12 | 22.6° | 1.083 |
| 6:12 | 26.6° | 1.118 |
| 7:12 | 30.3° | 1.158 |
| 8:12 | 33.7° | 1.202 |
| 9:12 | 36.9° | 1.250 |
| 10:12 | 39.8° | 1.302 |
| 11:12 | 42.5° | 1.357 |
| 12:12 | 45° | 1.414 |
How we calculate
The pitch is the rise over the run, scaled to 12. The angle is the arctangent of the rise over the run. The multiplier is the length of the sloped roof over the run: the square root of rise squared plus run squared, divided by the run. It is plain geometry, so it holds for any roof with that slope.
Ready to size the whole roof? Our roofing squares calculator uses these multipliers to count squares and shingle bundles.