Roof Pitch to Slope Angle
Also known as roof pitch to degrees · roof slope angle · 4 12 pitch
Worked example: 4:12 pitch → 18.4349 degrees — press Try an example to run it live, then adjust anything.
Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Try different units for next level excitement!
Roof Pitch to Slope Angle explained
Roofers do not talk in degrees, they talk in twelfths. A "4:12" roof rises 4 inches for every 12 inches of level run, and the number 12 is baked into the framing square, the rafter tables, and the shingle warranty. Converting to an angle is just , so 4:12 is 18.43°, 6:12 is 26.57°, and 12:12 is exactly 45°.
The angle version earns its keep when a tool needs it. Mitre saws, digital angle finders, solar array mounts and structural software all speak degrees, while the drawings speak twelfths. It is also the fastest way to check a manufacturer's limits: most asphalt shingles need a minimum 2:12 (9.46°) with a doubled underlayment, and 4:12 for standard application. Above about 6:12 you are into roof jacks and harnesses rather than walking the deck.
One trap: "pitch" in the strict old sense meant rise over the full span, so a roof with a 6 ft rise on a 24 ft span was "quarter pitch". Almost nobody uses that today, and this calculator uses rise per 12 of run, which is what the framing square measures.
Roof Pitch to Slope Angle formula
- = Slope angle (°)
- = Pitch (rise per 12 of run) (in 12)
Missing one of these? Work it out first, then come back
- Slope angle — Grade to Slope Angle, Ladder Setback and Angle (4-to-1 Rule)
- Pitch (rise per 12 of run) — Common Rafter Length from Run and Pitch, Roof Area from Footprint and Pitch