How to Find Roof Pitch With Your Phone (Degrees, %, x/12)
Short answer: lay the phone on a rafter or the roof surface with a level app and read the angle. Pitch in x/12 is 12 × tan(angle): 26.6° is 6/12, 18.4° is 4/12 and 33.7° is 8/12.
Three ways to say the same slope
- Degrees — the angle from horizontal.
- Percent grade — rise ÷ run × 100. 100% is 45°.
- Pitch x/12 — inches of rise per 12 inches of run, common in North America.
Quick conversion table
| Pitch | Degrees | Grade |
|---|---|---|
| 2/12 | 9.5° | 16.7% |
| 4/12 | 18.4° | 33.3% |
| 6/12 | 26.6° | 50% |
| 8/12 | 33.7° | 66.7% |
| 10/12 | 39.8° | 83.3% |
| 12/12 | 45° | 100% |
Measuring on the roof or in the attic
Lay the phone flat on the top edge of a rafter, or on the roof deck, along the slope. Wait a second for the reading to settle and tap Hold. If your phone case is uneven, set zero on a known level surface first.
Measuring from the ground with a photo
Stand in line with the gable end, hold the phone level and take a straight-on photo. Open the photo in a protractor app, put one arm on a horizontal line such as the eave and the other on the roof line.
Doing it with Anglora
Anglora's Level shows degrees, % grade and x/12 pitch at the same time, so there is nothing to convert. Use Photo mode for the ground method and save each reading with a name.
Frequently asked questions
What pitch is a 30° roof?
About 6.9/12, which is 57.7% grade.
Is 4/12 a low slope?
Yes. 4/12 is about 18.4°. Many shingle makers set their minimum slope around 2/12 to 4/12; check the product instructions.
Can I measure from the ground?
Yes, with a photo: stand level with the gable end, take a straight-on photo and measure the roof line against a horizontal line.
Related guides
Get Anglora: protractor, camera angle finder and level (Google Play)