Roof pitch is the measure of the slant of your roof. It is one of the many important elements of your roof, Roof pitch is one of the most visible aspects of a roof. It’s the measure of the steepness of a roof, or its slope. Roof pitch is expressed as a ratio of the roof’s vertical rise to its horizontal span, or “run”.
The most commonly used roof pitches fall in a range between 4/12 and 9/12. Pitches lower than 4/12 have a slight angle, and they are defined as low-slope roofs. Pitches of less than 2/12 are considered flat roofs, even though they may be very slightly angled.
Roof pitch calculation