Roof pitch vs degrees: which should you use and why?
Short answer. Pitch and degrees describe the same slope in different units: pitch is rise per 12 inches of run, and degrees is the angle from level. Use pitch for anything roofing, since building codes, shingle instructions and insurance estimates are written in x/12; use degrees mainly when a phone app or product sheet gives you an angle.
Why roofers stick with pitch
- It matches how roofs are built. Framers lay out rafters with a framing square using rise and run, so x/12 comes straight from the framing.
- Codes use it. Minimum slopes in the residential code are written as units of rise per 12, such as 2/12 for asphalt shingles.
- Estimates use it. Insurance and contractor estimates price steep slope labor by pitch bands, commonly starting around 7/12.
- Manufacturers use it. Shingle instructions switch to special fastening above roughly 20/12 or 21/12, not at an angle.
Why the two do not move together
Pitch increases in equal steps, but the angle does not. Going from 2/12 to 4/12 adds about 9 degrees; going from 10/12 to 12/12 adds only about 5. That is why a roof that looks only a little steeper in degrees can be a full pitch steeper on paper, and why an app reading of 30 degrees means a 7/12, not a 6/12.
Where degrees show up
- Phone inclinometer apps and digital angle finders.
- Solar panel mounting specs and some skylight instructions.
- Architectural drawings from outside the United States.
Converting
Degrees = inverse tangent of (rise ÷ 12). Pitch = 12 × tangent of the angle. Handy anchors: 4/12 is 18.4, 6/12 is 26.6, 8/12 is 33.7 and 12/12 is 45. When you talk to a roofer, translate to x/12 so everyone is using the same language. See how roofers measure a roof.