Roof Pitch Calculator
Calculate a roof's pitch angle and slope percentage from its rise and run.
Calculate a roof's pitch angle and slope percentage from its rise and run.
How Roof Pitch Calculator Works
Roof pitch is conventionally expressed as rise over a run of 12 inches (like "6/12") — the calculator converts that ratio into the actual angle in degrees using the arctangent function, and also expresses it as a slope percentage.
Who Uses Roof Pitch Calculator and Why
- Converting a measured rise and run into the standard "X/12" pitch notation used by roofers and contractors.
- Getting the actual angle in degrees for a roof design before running it through the Roofing Calculator's pitch multiplier.
- Checking whether an existing roof's pitch falls in a common residential range.
Mistakes to Avoid
- Leaving run at a value other than 12 when trying to get a standard "X/12" style reading — conventional pitch notation is always expressed against a 12-inch run, so changing the run value produces a technically correct angle but not a standard pitch fraction.
- Confusing pitch (a ratio, like 6/12) with angle in degrees (like 26.6°) — they describe the same slope but aren't numerically interchangeable, and roofing material specs sometimes reference one or the other.
- Measuring rise and run from an unreliable reference (like eyeballing a roof from the ground) rather than a physical measurement or accurate architectural drawing.
Tips for Best Results
- If you're feeding a result into the Roofing Calculator, keep run at 12 so the rise value you get directly matches that calculator's "rise per 12" field.
- A steeper pitch sheds water and snow more effectively but also increases true roof surface area (and material cost) compared to a shallower pitch of the same footprint.
Fixing Common Problems
My pitch doesn't look like a standard fraction (like 6/12). — Make sure run is set to 12 — standard roofing pitch notation always expresses rise relative to a 12-inch run, so any other run value will produce a correct angle but not a conventional pitch fraction.
Terms Explained
Pitch: A roof's steepness expressed as inches of rise per 12 inches of horizontal run (e.g., "6/12").
Slope percentage: Roof steepness expressed as a percentage (rise divided by run, times 100) rather than as a rise-per-12 ratio.