Wheelchair Ramp Slope Calculator
Work out the exact ramp length, slope ratio, gradient, and ADA compliance needed for any vertical rise. Enter your rise height and target slope ratio to see the full working instantly.
Ramp Details
Enter the vertical rise and target slope ratio to calculate the ramp length
The total vertical height the ramp needs to climb, e.g. from ground level to a doorstep.
For every 1 unit of rise, the ramp run extends this many units. 1:12 is the ADA maximum for new construction.
Your Ramp Specification
Length, gradient, angle, and ADA compliance check
Enter your rise height and target slope ratio above and click Calculate Ramp Length to see the required ramp length, gradient, and ADA compliance.
Understanding Ramp Slope & Gradient
Ramp slope is expressed as a ratio of rise to run: how much vertical height is gained for a given horizontal distance. A shallower ratio, like 1:20, is easier to navigate than a steeper one, like 1:8, but it requires significantly more horizontal space.
📐 The Slope Formula
To find the horizontal run needed, multiply the rise by the ratio denominator. The actual sloped surface length is then found using the Pythagorean theorem, since the ramp surface is the hypotenuse of a right triangle.
Run = Rise × Ratio Denominator
The gradient as a percentage is simply rise divided by run, multiplied by 100, while the angle in degrees comes from the arctangent of rise over run.
♿ ADA Compliance Basics
For new construction in the United States, the ADA caps the running slope at 1:12 and limits any single ramp run to a maximum rise of 30 inches before a level landing is required.
Max Rise per Run = 30 in
Landings must be at least 60 inches long, and the ramp itself needs a minimum clear width of 36 inches between handrails.
Ramp Length by Rise and Slope Ratio
These are the minimum ramp run lengths needed for common rise heights at the ADA maximum 1:12 ratio and the more comfortable 1:16 and 1:20 ratios.
| Rise Height | Run at 1:12 | Run at 1:16 | Run at 1:20 |
|---|---|---|---|
| 6 in | 6 ft | 8 ft | 10 ft |
| 12 in | 12 ft | 16 ft | 20 ft |
| 18 in | 18 ft | 24 ft | 30 ft |
| 24 in | 24 ft | 32 ft | 40 ft |
| 30 in | 30 ft | 40 ft | 50 ft |
| 36 in | 36 ft (needs landing split) | 48 ft | 60 ft |
Wheelchair Ramp FAQ
Everything you need to know about ramp slope ratios, ADA requirements, and how to plan a safe, compliant wheelchair ramp.
The ADA requires a maximum running slope of 1:12 for new construction, meaning for every 1 inch of vertical rise, the ramp must extend at least 12 inches in length. A gentler slope, such as 1:16 or 1:20, is easier for wheelchair users to navigate and is recommended wherever space allows.
Multiply the rise (the vertical height to be climbed) by the slope ratio denominator. For example, with a 1:12 ratio and a rise of 30 inches, the ramp run needed is 30 x 12 = 360 inches, or 30 feet, not counting the slightly longer sloped surface length itself.
Under ADA guidelines, a single ramp run should not rise more than 30 inches before a level landing at least 60 inches long is required. This limits how steep and how long any single uninterrupted section of ramp can be before users get a flat resting point.
Any slope steeper than 1:12 (about 8.3%, or roughly 4.8 degrees) exceeds ADA new-construction requirements and is generally considered unsafe for unassisted wheelchair use. Existing or site-constrained ramps may sometimes use steeper slopes such as 1:10 or 1:8 only over very short rises, under specific exceptions.
ADA guidelines require a minimum clear width of 36 inches between handrails for a wheelchair ramp, though many designers use 42 to 48 inches to comfortably accommodate larger mobility devices and allow easier passing or turning.
Handrails are generally required on both sides of any ramp run with a rise greater than 6 inches or a horizontal length greater than 72 inches. Handrails should be mounted between 34 and 38 inches above the ramp surface, continuous along the run, and extend at least 12 inches beyond the top and bottom of the ramp.