ADA Ramp Calculator

Ramp slope, length, and rise are governed by accessibility codes and physics. For wheelchair ramps, the ADA (Americans with Disabilities Act) sets strict maximum slope requirements. For loading ramps and vehicle approaches, slope affects safety and feasibility.

Slope ratio formula: Slope = Rise ÷ Run

Slope percentage: Slope (%) = (Rise ÷ Run) × 100

Ramp length from rise and slope: Run = Rise ÷ Slope

Actual ramp length (hypotenuse): Length = √(Rise² + Run²)

Variable definitions:

• Rise — the total vertical height change (e.g. height of a door threshold above grade)
• Run — the horizontal distance the ramp covers
• Slope — ratio of vertical to horizontal; a 1:12 slope = 1 inch of rise per 12 inches of run = 8.33%
• Length — actual surface distance along the ramp (always longer than Run by the Pythagorean difference)

ADA wheelchair ramp standards:

• Maximum slope: 1:12 (1 inch rise per 12 inches run = 8.33%)
• Maximum rise per ramp section: 30 inches (760 mm)
• Minimum width: 36 inches (915 mm) clear
• Landing requirements: At least 60″ × 60″ at top and bottom, and every 30″ of rise
• Edge protection: Curbs or rails required if drop-off exists on sides

Commercial loading ramp slopes:

• Walk-on loading ramp: max 10–14% (6°–8°)
• Pallet jack ramp: max 7% (4°)
• Forklift ramp: max 8–10% (5°–6°)
• Vehicle ramp (truck/van): max 15–20%

Worked example — ADA wheelchair ramp: Door threshold is 18 inches above grade.

• At 1:12 slope: Run = 18 × 12 = 216 inches = 18 feet
• Actual ramp surface length: √(18² + 216²) = √(324 + 46,656) = √46,980 = 216.75 inches ≈ 18.06 feet
• Landings: 18 inches rise in one run is within the 30-inch limit — one landing at top and one at bottom suffices
• Total space required: 18 ft ramp + 5 ft bottom landing + 5 ft top landing = 28 feet of horizontal space

For a 36-inch rise (3 ft), you would need two ramp sections with a mid landing, totaling 36 horizontal feet of ramp.