Grade Slope Percentage Calculator

The universal way civil engineers express slope

Grade percentage is the standard method for expressing slope on roads, ramps, drainage pipes, and site grading plans - a simple rise-over-run ratio expressed as a percentage.

Worked example

For a 1-unit rise over a 20-unit run:

Grade = (1/20) x 100 = 5.0% grade (2.862 degrees)

Application	Typical Maximum Grade
Highway design	6-8%
ADA accessibility ramps	5% (1:20) or less
Steep driveways	Up to 15-20%

This 5% result exactly matches the maximum grade commonly specified for ADA-compliant accessibility ramps intended for unassisted wheelchair use, a useful real-world reference point.