Gradient & Slope Calculator
Calculate slope percentage, angle, and rise-to-run ratio for construction and ADA compliance.
Calculating roof pitch? Try our Rafter Calculator for rafter length and angles.
Input
Result
Formulas
Slope% = (Rise / Run) × 100
Angle = arctan(Rise / Run)
Slope Length = √(Rise² + Run²)
ADA: Max slope 8.33% (1:12), max rise 30" before landing required
Understanding Gradient & Slope
Slope and gradient describe the steepness of a surface, expressed as a percentage, angle, or ratio. In construction, road design, and ADA compliance, accurately calculating slope is essential for safety and code adherence. Whether you're designing a wheelchair ramp, grading a driveway, or setting pipe slopes, understanding these measurements ensures your project meets requirements.
Formulas
These formulas are interrelated — knowing any two of rise, run, angle, or slope percentage lets you calculate the others. The slope length (hypotenuse) is always the longest side of the right triangle formed by rise and run.
How to Calculate Slope
Frequently Asked Questions
How do I calculate slope percentage?
Slope percentage = (Rise ÷ Run) × 100. For example, a ramp that rises 1 foot over a 12-foot run: (1 ÷ 12) × 100 = 8.33% slope. This is the maximum allowed for ADA-compliant wheelchair ramps.
What is the ADA maximum slope for a wheelchair ramp?
ADA standards require a maximum slope of 1:12 (8.33%) for wheelchair ramps. The maximum rise for any single ramp run is 30 inches (762 mm), after which a level landing is required. For existing sites, steeper slopes up to 1:8 (12.5%) may be permitted for short rises.
How do I convert slope to angle?
Angle = arctan(Rise ÷ Run) = arctan(Slope% ÷ 100). For a 100% slope (45°): arctan(1) = 45°. For an 8.33% ADA ramp: arctan(0.0833) ≈ 4.76°. You can also use: Angle = arctan(Slope% / 100) × (180/π).
What is a 1:12 slope?
A 1:12 slope means 1 unit of vertical rise for every 12 units of horizontal run. This equals 8.33% grade and approximately 4.76°. It is the standard maximum slope for ADA wheelchair ramps. For every inch of rise, you need at least 12 inches (1 foot) of ramp run.
What is the difference between grade and slope?
Grade and slope both express steepness, but grade is expressed as a percentage (Rise/Run × 100) while slope can be expressed as a ratio (Rise:Run), angle (degrees), or percentage. In road construction, "6% grade" means a 6% slope — the road rises 6 feet for every 100 feet of horizontal distance.