Roof Pitch Calculator
Find a roof's pitch (x/12) from its rise and run, or from its angle, with the angle, grade and slope factor.
Change the values and press Calculate to work out your own figures.
From rise and run
Enter the rise and the run.
Show the working
- pitch = rise ÷ run × 12
- angle = atan(rise ÷ run)
From the angle
Enter the roof's angle.
Show the working
- pitch = rise ÷ run × 12
- angle = atan(rise ÷ run)
How to use it
Enter the rise and the run. Enter the roof's angle.
Lengths can be decimals, fractions or tape entries such as 12' 6 1/2" (in feet or inches). Prices are optional.
Key facts
pitch = rise ÷ run × 12 (/12); angle = atan(rise ÷ run); slope factor = √(1 + (pitch ÷ 12)²)
Pitches
Under 2/12 is a flat roof for shingles (use membranes); 4/12–9/12 is typical; over 9/12 is steep and harder to walk.
Questions
What angle is a 4/12 roof?
18.43°.
What pitch is 35°?
8.4/12.
Formulas
pitch = rise ÷ run × 12 (/12); angle = atan(rise ÷ run); slope factor = √(1 + (pitch ÷ 12)²)
Sources
Limitations
- Material densities are typical values (the midpoint of the commonly published range); real loads vary with moisture, grading and compaction, so check with your supplier or type in their density.
- Tank results are the geometric volume; real tanks have wall thickness and fittings.