Ramp Slope Calculator

In length mode, enter the rise and a slope ratio — 1:12 is the ADA maximum, with 1:16 and 1:20 presets for gentler ramps — and get the required horizontal run. In slope mode, enter a rise and run to get the ratio, angle, and percent grade, with a flag whenever the result is steeper than 1:12.

Common uses

• Size a wheelchair ramp for a 24 in porch rise
• Check whether an existing ramp meets the ADA slope limit

Example

24 in rise at 1:12

24 ft of ramp (288 in of run)

Limitations

• ADA also requires landings every 30 in of rise, minimum widths, and handrails — this tool only covers slope

How long does a ramp need to be for a 24 inch rise?

24 ft at the ADA 1:12 maximum — one foot of run for every inch of rise. A gentler 1:16 slope stretches it to 32 ft and 1:20 to 40 ft, so the space you have often decides the slope for you.

What is the maximum ADA ramp slope?

1:12, meaning 1 in of rise per 12 in of run. A single ramp run may also climb no more than 30 in before a level landing, and handrails are required once a run rises more than 6 in — this tool covers the slope only.

How do I convert a ramp slope to a percent grade?

Divide rise by run and multiply by 100. A 1:12 ramp is an 8.33% grade at 4.76°, 1:16 is 6.25%, and 1:20 is a 5% grade — the point below which a walking surface is no longer treated as a ramp.

Can a residential ramp be steeper than 1:12?

Often, yes — ADA limits apply to public accommodations and commercial facilities, not to a private home, and portable and threshold ramps are commonly rated at 2:12 or 3:12 for assisted use. Anything steeper than 1:12 is hard to self-propel and gets flagged here, so treat it as a deliberate trade-off.

Are my ramp measurements sent to a server?

No. The slope, angle, and length math runs in your browser — the rise and run you enter are never transmitted or saved.