What does roof pitch mean?
Short answer. Roof pitch is how steep a roof is, written as inches of vertical rise for every 12 inches of horizontal run. A 6/12 pitch rises 6 inches per foot, about 26.6 degrees; a 12/12 pitch rises a foot per foot, which is 45 degrees.
How pitch is written
You will see it as 6/12, 6:12, 6 in 12, or just "a 6 pitch." The second number is always 12 because run is measured per foot. The first number is the rise in inches over that foot.
Rise and run
- Run: horizontal distance, measured level, from the outside wall to the point under the ridge.
- Rise: vertical height gained over that distance.
- Span: the full width between outside walls, twice the run on a symmetrical gable.
Common pitches in degrees
- 3/12: 14.0 degrees
- 4/12: 18.4 degrees
- 6/12: 26.6 degrees
- 8/12: 33.7 degrees
- 10/12: 39.8 degrees
- 12/12: 45.0 degrees
Why it matters to a homeowner
- Which materials are allowed: asphalt shingles need at least 2/12, with double underlayment up to 4/12.
- Roof area and cost: steeper roofs have more surface area over the same footprint, and above about 7/12 or 8/12, crews need extra safety equipment.
- Drainage: steeper roofs shed water and debris faster.
- Appearance and attic space.
Strictly speaking, pitch and slope are defined differently, but roofers, measurement reports and adjusters all use pitch to mean the x/12 slope, so you can treat them as the same number. See roof anatomy explained and how roofers measure a roof.