How do you find roof pitch with a level, a square or a phone?
Short answer. The simplest tool method is a level and tape: hold the level horizontal against the roof or a rafter, mark 12 inches from the contact point, and measure straight down or up to the roof surface; that number over 12 is your pitch. A speed square or a phone level app reading degrees gives the same answer faster.
Level and tape
- Work from a ladder at the rake edge, or inside the attic on a rafter. Avoid getting on the roof.
- Rest one end of a 2 foot level on the roof surface or rafter and hold it perfectly level.
- Mark the level at 12 inches from the contact end.
- Measure straight between the 12 inch mark and the roof or rafter surface.
- That measurement is the rise. 6 inches means a 6/12 pitch.
Speed square
Many speed squares have a scale for common rafter pitches. Place the pivot point against the rafter, rotate the square until its edge is plumb or level as the instructions describe, and read the pitch from the scale. Practice on a known angle first.
Phone level app
Lay the phone along a rafter or the rake board and read the angle in degrees. Convert it:
- 18.4 degrees: 4/12
- 22.6 degrees: 5/12
- 26.6 degrees: 6/12
- 30.3 degrees: 7/12
- 33.7 degrees: 8/12
- 39.8 degrees: 10/12
- 45 degrees: 12/12
Tips for accuracy
- Measure on a straight section, not a sagging rafter or a bump in the shingles.
- Take two or three readings and average them.
- Measure each roof section separately; porches and additions often differ.
See how roofers measure a roof and roof anatomy explained for what to do with the number.