What is a roof pitch angle?
Converting pitch to angle and back
On a phone calculator in scientific mode, divide the rise by 12 and press the inverse tangent key (atan). For 8/12, 8 divided by 12 is 0.667, and its arctangent is about 33.7 degrees. To go the other way, multiply 12 by the tangent of the angle: 30 degrees gives a rise of about 6.9, so a 30 degree roof is just under 7/12.
Common pitches as angles
- 3/12: about 14.0 degrees
- 4/12: about 18.4 degrees
- 6/12: about 26.6 degrees
- 8/12: about 33.7 degrees
- 10/12: about 39.8 degrees
- 12/12: 45 degrees
What angle should a roof be?
The roofing material sets the floor. Under the International Residential Code, asphalt shingles need at least 2/12 (about 9.5 degrees) and two layers of underlayment until 4/12 (about 18.4 degrees). Lapped metal panels without sealant need 3/12 (about 14 degrees), while standing seam metal can go nearly flat. Slate needs 4/12, and clay or concrete tile needs 2.5/12 with double underlayment.
Above those minimums, the right angle is a balance. In rainy Georgia, roofs from roughly 26 to 37 degrees (6/12 to 9/12) shed heavy downpours and debris well and are still walkable for maintenance. Angles above about 40 degrees look dramatic but cost more to install and repair because crews need staging and harnesses.
Where you will see angles instead of pitch
Solar designers, phone apps and some engineering drawings use degrees; roofers and estimates almost always use pitch. Our measuring guide shows how pitch feeds the roof area, and metal roofing in Georgia covers low-angle metal options.