Roof pitch calculator
Enter how far the roof rises over a given horizontal run and get the pitch in degrees, percent slope, and the X-in-12 ratio roofers use. To measure a roof you can't reach, hold an iPhone against a rafter in the attic and read the angle directly.
Degrees
18.4°
Pitch
4:12
Slope
33.3%
Pitch is shown as rise per 12 of run. Formula: degrees = arctan(rise ÷ run).
How to measure roof pitch
You can measure pitch three ways: hold a phone flat against the roof slope or an attic rafter and read the angle; rest a level on the slope and measure the drop at the 12-inch mark; or measure a square-on photo of the roofline with a camera protractor. The attic method is the safest accurate option — rafters share the roof's exact slope and you never leave the floor. See the full walkthrough in how to measure roof pitch.
| Pitch | Degrees | Percent slope |
|---|---|---|
| 1:12 | 4.8° | 8.3% |
| 2:12 | 9.5° | 16.7% |
| 3:12 | 14.0° | 25.0% |
| 4:12 | 18.4° | 33.3% |
| 6:12 | 26.6° | 50.0% |
| 9:12 | 36.9° | 75.0% |
| 12:12 | 45.0° | 100.0% |
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