Ramp Slope Calculator
Calculate wheelchair ramp slope, length, run, and grade. Enter rise and choose ADA or custom slope ratio to design compliant ramps.
What is a Ramp Slope Calculator?
A ramp slope calculator helps you design wheelchair ramps, loading ramps, and other inclined accessways that comply with ADA (Americans with Disabilities Act) standards and local building codes. By entering the vertical rise and selecting the desired slope ratio, you instantly get the required ramp length, horizontal run, slope angle, and grade percentage.
Whether you are building a home accessibility ramp, a commercial wheelchair ramp, or a loading dock, this tool ensures your ramp meets safety requirements for slope, landing size, and clearance.
Ramp Slope Formula
The ramp slope is calculated as the ratio of rise to run:
$$ \text{slope ratio} = \frac{\text{rise}}{\text{run}} $$
The ramp length (the inclined surface) is found using the Pythagorean theorem:
$$ L = \sqrt{\text{rise}^2 + \text{run}^2} $$
The slope angle is the inverse tangent of the rise-to-run ratio:
$$ \theta = \arctan\left(\frac{\text{rise}}{\text{run}}\right) $$
And the grade percentage is:
$$ \text{grade (\%)} = \frac{\text{rise}}{\text{run}} \times 100\% $$
ADA Ramp Requirements
The ADA Standards set specific requirements for public ramps. The maximum slope for new construction is 1:12 (one inch of rise for every 12 inches of run), which corresponds to a 4.8-degree angle. The comfortable slope is 1:16, and the minimum slope before a ramp is no longer considered a ramp is 1:20. For residential or assisted-use ramps, 2:12 is acceptable, and for loading unoccupied chairs, 3:12 is permitted. Landings of at least 60 inches are required at the top, bottom, and any turns in the ramp.
For related construction calculations, try the Stair Calculator or the Concrete Calculator for foundation work.
Frequently Asked Questions
What is the maximum slope for an ADA-compliant ramp?
The maximum slope for ADA-compliant ramps in new construction is 1:12, meaning one inch of vertical rise requires at least 12 inches of horizontal run. This corresponds to a 4.8-degree angle or a 8.33% grade. Steeper slopes of 1:10 or 1:8 are permitted only in existing sites with space limitations, with stricter maximum rise limits.
How long should a wheelchair ramp be?
The ramp length depends on the vertical rise and chosen slope. For a 30-inch rise at the ADA maximum slope of 1:12, you need a ramp that is at least 30 feet long. At the comfortable 1:16 slope, the same rise requires a 40-foot ramp. Use this calculator to find the exact length for your specific rise and slope requirements.
What is a 100% slope?
A 100% slope means the rise equals the run, which corresponds to a 45-degree angle. This is exceptionally steep for a ramp and would not be ADA compliant. Most wheelchair ramps have slopes between 5% and 8.33%.
Do I need landings on a ramp?
Yes, ADA requires level landings at the top and bottom of every ramp section. If the ramp changes direction (a 90-degree turn), a minimum 60x60 inch landing is required. For switchback ramps, even larger landings may be needed. Landings must be at least as wide as the ramp and a minimum of 60 inches long.
What is the minimum width for a wheelchair ramp?
The minimum clear width for an ADA-compliant wheelchair ramp is 36 inches (91.5 cm). This allows enough space for a standard wheelchair to pass comfortably. Handrails should be mounted so they do not reduce this clear width.
When are handrails required on a ramp?
Handrails are required on both sides of a ramp when the rise exceeds 6 inches or the run exceeds 72 inches (6 feet). Handrails must be between 34 and 38 inches high and extend at least 12 inches beyond the top and bottom of the ramp.
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