Roof Pitch Calculator
Enter a roof's rise (vertical height gained) over a standard run (typically 12 inches) to calculate the pitch as a ratio and as an angle in degrees.
How the Roof Pitch formula works
Pitch as a ratio, and converted to an angle:
Pitch = Rise / Run (commonly expressed as "rise/12") Angle = arctan(Rise / Run)
Step-by-step calculation
- Measure the rise (vertical height) over a run of 12 inches — the standard way roof pitch is expressed.
- Express the pitch as "rise/12" (like 6/12).
- Take the arctangent of rise divided by run to find the angle in degrees.
Worked example
A roof rising 6 inches over a 12-inch run: Pitch = 6/12. Angle = arctan(6/12) = arctan(0.5) ≈ 26.57°.
Frequently asked questions
What's considered a steep roof pitch?
Pitches below about 4/12 are often called low-slope, 4/12 to 9/12 is a common moderate range for residential roofs, and anything above roughly 9/12 is generally considered steep — though what counts as appropriate depends on climate, material, and local building code.
Why is roof pitch expressed as 'X/12' instead of degrees?
It's a longstanding construction convention tied to how roofs are framed and measured on site — a rise-over-a-12-inch-run ratio is easy to check directly with a level and tape measure, without needing to calculate an angle.