Roof Pitch Calculator
Calculate roof pitch as a ratio (x-in-12), slope angle in degrees, and percent grade from a measured rise and run.
About the Roof Pitch Calculator
Roof pitch describes how steep a roof is, most commonly expressed in the U.S. as the number of inches a roof rises for every 12 inches of horizontal run (a "6-in-12" roof, for example). This calculator converts any measured rise and run into that standard pitch ratio, plus the equivalent slope angle and percent grade.
Formula: Pitch (x-in-12) = (Rise ÷ Run) × 12; Slope Angle = arctan(Rise ÷ Run); Percent Slope = (Rise ÷ Run) × 100
To measure rise and run on an existing roof, hold a level out horizontally from the roof surface for exactly 12in (the run), then measure the vertical gap down to the roof surface at that point (the rise). Most residential roofs fall between about 4-in-12 and 9-in-12 — steeper pitches shed snow and water faster and often look more dramatic, but need more roofing material, steeper safety precautions to work on, and can push framing and rafter costs higher.