Roof pitch explained — rise over run, and how a 6:12 pitch becomes an angle and a slope multiplier
Roof pitch is rise over run: a 6:12 roof climbs 6″ for every 12″ of horizontal run. That single ratio fixes everything else — the rafter length (√(6²+12²)=13.42″ per foot of run), the angle (26.6°), the grade (50%), and the 1.118 slope multiplier used to size materials.
What this diagram shows
Diagram of a gable roof with a right triangle on one slope showing what roof pitch means. Pitch is the vertical rise per 12 inches of horizontal run, so a 6:12 pitch rises 6 inches for every 12 inches of run. The sloped top edge is the rafter; by the Pythagorean theorem it measures the square root of 6 squared plus 12 squared, which is 13.42 inches per 12 inches of run. The same 6:12 pitch equals a roof angle of 26.6 degrees, a 50 percent grade, and a slope multiplier of 1.118 that converts flat footprint area to true sloped roof area.
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Roof Pitch Calculator
Convert roof pitch between rise:run, degrees, percent grade and slope multiplier. Get sloped roof area, rafter length and code-allowed coverings. Free.
