Elevation Grade Calculator
Calculate percent grade, slope angle and actual slope distance for a driveway, ramp, road or drainage run from its rise and horizontal run.
About the Elevation Grade Calculator
Grade (or slope) describes how steeply a surface rises or falls, and shows up constantly in site work — driveway slopes, wheelchair ramps, road grades and drainage pipe runs are all specified this way. This calculator converts a measured rise and horizontal run into percent grade, slope angle and the actual sloped distance.
Formula: Percent Grade = (Rise ÷ Run) × 100; Slope Angle = arctan(Rise ÷ Run); Slope Distance = the square root of (Rise² + Run²), from the Pythagorean theorem, since the sloped surface is the hypotenuse of the rise and run
ADA-compliant ramps generally require a maximum running slope of 1:12 (about 8.3%), driveways are commonly kept under a 15-20% grade for vehicle clearance and traction, and gravity drain pipe is often targeted around a 1-2% grade to keep flow moving without settling solids. Always check the specific code or manufacturer requirement for your application, since allowable grades vary widely by use.