Wheelchair Ramp Calculator — ADA Slope

A two-foot step at the front door turns into twenty-four feet of ramp. That surprises almost everyone, and it is why ramps are planned from the rise rather than eyeballed. Enter how high the ramp has to climb. This calculator gives its length at the slope you choose, how many runs and landings it needs, the total length in a straight line, and whether it meets the 2010 ADA Standards for Accessible Design.

It also answers the question that usually comes next: will it fit? Add the straight length you have on site and it says whether the ramp fits, and roughly how much a switchback layout would save if it does not.

Worked Example: A 24-Inch Porch at 1:12

The calculator opens with a 24 in rise at 1:12, the steepest slope the ADA allows for a new ramp. It reports:

• Ramp length: 24 ft of horizontal run, 24 ft 1 in measured along the slope, at 4.76°
• Runs and landings: one run, since it rises no more than 30 in, with a 5 ft landing at the top and the bottom
• Overall: 34 ft in a straight line, with handrails required on both sides because the run rises more than 6 in

Load Sample moves on to a 450 mm rise in metric (8.45 m overall), then a 36 in rise that has to split into two 18 ft runs and needs 51 ft against 40 ft available. The tool suggests a switchback of about 28 ft for that one. Last comes a 150 mm step at a gentle 1:20, which needs no handrails.

How the Math Turns a Rise Into Runs and Landings

At a 1:N slope the horizontal length is simply the rise times N. No single run may rise more than 30 in (760 mm), so the rise is split into equal runs, and every run gets a level landing at least 5 ft (1525 mm) long at each end. The total is the sloped runs plus all the landings. Switching between inches and millimetres converts the numbers you entered. Steeper slopes are flagged: 1:10 and 1:8 are allowed only for small rises in existing buildings with no room, and the tool says which applies.

Limits: What the ADA Check Does Not Cover

The check covers the parts of ADA §405 that depend on the numbers here: running slope, rise per run, landing length and when handrails are needed. It does not check the cross slope (no more than 1:48), edge protection, the handrail height of 34 to 38 in, or the surface. Local building codes can be stricter, and the UK, Canada and India each publish their own gradients. For a home ramp, 1:16 or 1:20 is much easier to push up than the 1:12 maximum. A rise must be entered as a positive height, or the tool says: “Rise must be a height in inches greater than 0, measured from the lower ground to the top surface.”