Ramp Calculator
Calculate ramp length, slope, and ADA compliance.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Ramp Calculator
This calculator gives you the ramp length along the slope, horizontal run, slope angle, slope percentage, and ADA compliance status. Here is how to use it:
- Enter the total rise. Measure from the lower surface to the upper surface in inches. For a door threshold that is 6 inches above a patio, enter 6. For a loading dock 24 inches above grade, enter 24.
- Choose the slope ratio. The ratio describes how many inches of horizontal run are required per inch of rise. A 1:12 slope means 12 inches of run for every 1 inch of rise. The ADA maximum for new construction is 1:12. A 1:16 or 1:20 slope is gentler and preferred where space allows. The 1:8 option is for non-ADA residential use only.
- Set the ramp width. ADA requires a minimum clear width of 36 inches between handrails. For wheelchairs, 44 inches or wider is recommended when two-way traffic is possible.
- Read your results. The primary result is the ramp length measured along the slope surface (the actual board length you need to cut). The breakdown shows the horizontal run (footprint on the ground), slope angle, slope percentage, and whether intermediate landings are required.
Results update as you type. Use Share to send your inputs to a contractor, or Copy to paste the result elsewhere.
About the Ramp Calculator
The ADA (Americans with Disabilities Act) sets clear standards for accessible ramps in public accommodations and commercial facilities. The maximum running slope is 1:12, meaning for every inch of rise the ramp must extend at least 12 inches horizontally. The minimum clear width is 36 inches. Any ramp with a rise greater than 6 inches must have handrails on both sides. When a ramp run exceeds 30 feet of horizontal length, a level rest landing at least 5 feet by 5 feet is required.
Ramp length (along the surface) is calculated using the Pythagorean theorem: the square root of rise squared plus run squared, then converted to feet. Slope angle uses the arctangent of rise divided by run. All calculations run in your browser. No data is stored or transmitted.
Note: ADA standards apply to commercial and public facilities. Residential ramps follow local building codes, which may differ. Always confirm requirements with your local building department before construction.
Frequently Asked Questions
What is the ADA maximum slope for a wheelchair ramp?
The ADA maximum running slope is 1:12, meaning 1 inch of rise for every 12 inches of horizontal run. This equals approximately 4.76 degrees or an 8.3% grade. For new construction, a gentler slope of 1:16 or 1:20 is recommended wherever space permits, as it reduces the effort required for wheelchair users. Slopes steeper than 1:12 do not meet ADA standards for public and commercial facilities.
How long does a ramp need to be for a 24-inch rise?
At the ADA maximum slope of 1:12, a 24-inch rise requires a minimum horizontal run of 24 feet (288 inches). The actual ramp surface length along the slope is approximately 24.08 feet (using the Pythagorean theorem). Because the run exceeds 30 feet only when the rise is greater than 30 inches at 1:12, a 24-inch rise at 1:12 does not require an intermediate landing. If you use a gentler 1:16 slope, the run increases to 32 feet, which does require one 5-by-5-foot landing.
When are landings required on a ramp?
ADA guidelines require a level rest landing whenever the horizontal run of a ramp segment exceeds 30 feet. Landings must be at least 60 inches (5 feet) long and at least as wide as the ramp. A landing is also required at the top and bottom of every ramp run and wherever the ramp changes direction. The landing at a door must be at least 60 inches long to allow a wheelchair user to open and pass through the door without rolling backward off the ramp.
What is the difference between ramp length and ramp run?
Ramp run is the horizontal distance measured flat on the ground from the bottom of the ramp to the top, like measuring with a tape measure along the floor. Ramp length (or surface length) is the actual distance along the sloped surface, which is the hypotenuse of the triangle formed by the rise and run. For a 1:12 slope the difference is small: a 24-foot run with a 2-foot rise gives a surface length of about 24.08 feet. The ramp length is what you use when ordering lumber or materials for the ramp surface.