How to Measure Roof Pitch: A Step-by-Step Guide
A step-by-step method for measuring your roof's rise and run safely from the attic, plus how to read the result as a standard pitch ratio.
Roof pitch is always expressed as rise over a fixed run — usually 12 inches — and the most accurate, safest way to measure it doesn't involve climbing onto the roof at all.
The attic method
- Go into the attic where a rafter is exposed and accessible.
- Hold a torpedo level flat against the underside of the rafter until it reads perfectly horizontal.
- Measure exactly 12 inches out along the level from the rafter.
- At that 12-inch mark, measure straight down to the top edge of the rafter — that vertical measurement is your rise.
Reading the result
If your vertical measurement is 6 inches, your pitch is "6/12" — a 6-inch rise for every 12 inches of run. This converts to a 26.6° angle and a 50% slope, both of which a pitch calculator can derive automatically once you have the raw measurement.
Why not just eyeball it from the ground?
Roofs consistently look shallower than they actually are when viewed from a distance — an eyeballed guess is rarely accurate enough for ordering roofing material or discussing a project with a contractor. Always take an actual measurement.
Once you have your rise and run, the Roof Pitch Calculator converts them instantly into pitch ratio, angle, slope percentage, and — if you add your roof's dimensions — rafter length and surface area.