Roof Pitch Calculator
Roof pitch ratio, angle, and multiplier.
- 100% free
- No sign-up
- Private — runs in your browser
- Instant results
Reading roof pitch
Roof pitch describes how steep a roof is, written as rise-over-run — for example 6:12, meaning the roof rises 6 inches for every 12 inches of horizontal travel. This calculator converts any rise and run into that ratio, the angle in degrees, and the slope multiplier used to size materials.
The slope multiplier
The area multiplier is √(rise² + run²) ÷ run. Multiply a roof's flat footprint by it to get the true sloped surface area — exactly what the roofing calculator needs to count shingles. A 6:12 roof has a multiplier of about 1.118, so its surface is roughly 12% bigger than its footprint.
FAQ
What counts as a steep roof?
Anything 9:12 (37°) or steeper is generally considered steep-slope and may need extra safety gear, different underlayment, and more waste allowance. Below about 2:12, most shingles aren't rated and you need a membrane or metal system instead.
What is the slope multiplier used for?
The multiplier, √(rise² + run²) ÷ run, converts a roof's flat footprint area into the actual sloped surface area. Multiply your building's footprint by it to estimate how much roofing material the pitched surface really needs.
How do I convert pitch to degrees?
The angle is the arctangent of rise divided by run, and the calculator shows it automatically. For example, a 6:12 pitch is about 26.6 degrees, while a 12:12 pitch is exactly 45 degrees.
Do I measure rise and run in the same units?
Yes, keep both in the same unit, since pitch is a ratio. The conventional run is 12 inches, so a rise of 6 inches over that 12-inch run gives the familiar 6:12 pitch.
Is the roof pitch calculator free, private, and mobile-friendly?
Yes, it is free with no sign-up, the math runs in your browser so nothing is uploaded, and it works on a phone right on the job site. Treat results as estimates and confirm structural details with a professional.