Slope & Grade Calculator — Rise Over Run
Convert between slope ratio, grade percentage, angle degrees, and roof pitch. Includes common slope references for ADA ramps, drainage, and roofing.
Slope % = (Rise / Run) x 100. Angle = arctan(Rise / Run). Pitch = Rise per 12 units of run.
Understanding Slope, Grade, and Pitch in Construction
Slope is expressed in four interchangeable formats in construction: slope ratio (rise:run), grade percentage (rise/run x 100), angle (degrees), and pitch (rise per 12 units of run). Each format is preferred in different contexts.
Grade percentage is most common for earthwork, drainage, and roads. A 2% grade means the surface drops 2 feet for every 100 feet of horizontal distance. Pitchis the standard for roofing — a 4/12 roof rises 4 inches for every 12 inches of run. Slope ratio is used for ADA compliance (1:12 max ramp slope) and retaining walls.
Common Construction Slopes
Key slopes to know: ADA ramps require 1:12 maximum (8.33%). Drainagearound foundations needs at least 1-2%. Driveways typically run 2-5%. Standard roof pitches range from 4/12 (18.4°) for minimum shingle roofs to 12/12 (45°) for steep designs. Flat roofs need a minimum 1/4" per foot (2.08%) for drainage.
Frequently Asked Questions
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