Roof Pitch Calculator App
Turn your smartphone into a digital roofing clinometer. Lay your phone flat against a rafter board or roofing deck to read pitch and degrees in real time.
How to Measure On Site With Your Phone
- 1Open this page on your smartphone Safari or Chrome browser.
- 2Remove bulky phone cases with uneven camera bumps, or lay a 12-inch wood scrap along the rafter first.
- 3Lay the edge of your phone flat against the bottom of a common rafter or roof deck.
- 4Read the pitch ratio ($X:12$) and degrees directly from the display dial.
RoofCal runs as an offline Progressive Web App. Install it directly to your home screen for instant zero-load access on any roofing site:
How the Phone Pitch Finder Works
The digital clinometer reads your phone’s built-in gyroscope (the same motion sensor that rotates the screen), converts the tilt angle to a roof pitch in real time, and displays all three notations at once: the X:12 ratio, the angle in degrees, and the grade percentage. On iPhones running iOS 13 or later the browser asks for motion-sensor permission once; Android Chrome picks up the sensor automatically. On desktops without sensors, the tilt simulator above lets you drag to any angle.
Getting an accurate reading: rest the phone (or a 12-inch straight scrap against it) flat on the underside of a common rafter — not a hip or valley, which run diagonally and read flatter. Remove bulky cases with uneven camera bumps, wait a second for the reading to settle, and expect roughly ±0.2° accuracy on a clean surface. For cutting layouts and permit drawings, verify with a level and tape measure using the standard measuring method rather than relying on the sensor alone.
Field uses: quick pitch takeoffs for material quotes, confirming pitch before ordering shingles or metal, checking a built roof against plan specs, and simple roof-report documentation — all without carrying a separate clinometer to the job.