What are roof pitches in angles?
Short answer. Roof pitches convert to angles with the arctangent of rise over 12. The common ones are 4/12 = 18.4 degrees, 6/12 = 26.6 degrees, 8/12 = 33.7 degrees, 10/12 = 39.8 degrees and 12/12 = 45 degrees.
Pitch to angle, low to steep
- 1/12: 4.8 degrees
- 2/12: 9.5 degrees
- 3/12: 14.0 degrees
- 4/12: 18.4 degrees
- 5/12: 22.6 degrees
- 6/12: 26.6 degrees
- 7/12: 30.3 degrees
- 8/12: 33.7 degrees
- 9/12: 36.9 degrees
- 10/12: 39.8 degrees
- 11/12: 42.5 degrees
- 12/12: 45.0 degrees
- 14/12: 49.4 degrees
- 16/12: 53.1 degrees
- 18/12: 56.3 degrees
- 24/12: 63.4 degrees
Why the angles are not evenly spaced
Each added inch of rise adds fewer degrees as the roof gets steeper. Going from 1/12 to 2/12 adds about 4.7 degrees, while going from 11/12 to 12/12 adds about 2.5. That is why a small reading error on a steep roof can be a whole pitch step off.
Why roofers use x/12 instead of degrees
- Building codes and shingle instructions state minimum slopes as x in 12.
- Rise per foot is easy to measure with a level and tape.
- Framing squares and speed squares are marked in rise per 12.
- Measurement reports and insurance estimates list pitch the same way.
Where angles are handy
Phone apps, digital angle finders and solar panel tilt specs use degrees. Convert with rise = 12 × tan(angle). See how roofers measure a roof and replacing your roof before solar.