ADA Ramp Slope Calculator
Find the minimum ramp length and landing requirements for an ADA-compliant wheelchair ramp, from the height it needs to rise.
Reviewed by the ToolNestr Editorial Team — July 2026
How the ADA ramp slope calculator works
A ramp's slope is expressed as a ratio, like 1:12, meaning 1 unit of rise for every 12 units of horizontal run. The ADA Standards for Accessible Design set 1:12 as the maximum running slope for a ramp serving an accessible route, so the minimum ramp length is simply the total rise multiplied by that ratio.
The calculator also applies the ADA's landing rule: no single ramp run may rise more than 30 inches before a level landing is required. For a total rise taller than that, it splits the climb into multiple 30-inch-or-less runs and inserts a landing between each one, since a landing lets a wheelchair user rest and change direction on a flat, no-slope surface.
Landings themselves must be at least as wide as the ramp and at least 60 inches long, per the ADA standard, at the top and bottom of every run. This tool estimates ramp length and landing count for planning; final ramp width, handrail requirements, edge protection, and landing placement should be confirmed against the full ADA standard and your local accessibility code.
Slope, rise, and landing figures follow the 2010 ADA Standards for Accessible Design, section 405 (Ramps).
Enter the rise
The total height the ramp needs to climb, in inches.
Pick the slope
1:12 is the ADA maximum; gentler slopes like 1:16 or 1:20 are easier to use.
Read the layout
See the minimum length, number of runs, and landings needed.
The formula explained
Minimum length at 1:12
length = rise × 12. A 24″ rise: 24 × 12 = 288″ = 24 ft.
Runs and landings
Max 30″ rise per run: ceil(24⁄30) = 1 run, so no intermediate landing is required for this rise.
Slope angle
angle = atan(1⁄12) = 4.76° — the maximum angle allowed on an ADA ramp.
Worked example
A porch with a 42″ rise, at the ADA 1:12 maximum slope.
Designing an accessible ramp
Gentler is better where space allows
1:12 is the maximum, not the target. A 1:16 or 1:20 slope is easier to push a wheelchair up and safer on ice or rain, if you have the extra length to spare.
Plan landings early
Landings take real floor space at the top, bottom, and any turn. Account for them in your site plan before committing to a ramp path.
Handrails and edge protection
Ramps rising more than a few inches typically need handrails on both sides and edge protection to keep a wheel or cane tip from sliding off — details this length estimate does not cover.
Confirm local code
State and local accessibility codes sometimes add requirements beyond the federal ADA standard. Check with your building department before finalizing the design.
Real-world context
A single-step threshold ramp is one of the most common small jobs. A 7-inch rise over a door threshold at the ADA 1:12 maximum needs 7 × 12 = 84 inches, or exactly 7 feet of ramp, with no landing required since it falls well under the 30-inch single-run limit — a length that fits in most entryways without redesigning the approach.
A full-story rise tells a different story. Climbing a 60-inch porch or deck height at 1:12 needs 60 × 12 = 720 inches, or 60 feet of ramp, split into ceil(60⁄30) = 2 runs with 1 intermediate landing — enough total length that many homeowners switch to a switchback layout with a turning landing to fit the ramp on the available lot, rather than running it straight out from the house.
Choosing a gentler slope changes the math directly. An 18-inch rise at the ADA maximum 1:12 needs 18 feet of ramp, but the same rise at a gentler 1:16 slope needs 18 × 16 = 288 inches, or 24 feet — 6 feet longer, but noticeably easier to self-propel for a wheelchair user, which is why many accessibility consultants recommend 1:16 or 1:20 whenever the site has the extra room.
Common misconceptions
"1:12 is a good, comfortable slope to build to." It's the legal ceiling, not a design target. A ramp at exactly 1:12 is the steepest slope the ADA permits, and it can still be tiring to self-propel up, especially over long runs. Building at 1:16 or 1:20 whenever space allows makes the ramp noticeably easier and safer to use.
"A short ramp does not need landings." Landings are required at the top and bottom of every ramp, regardless of length. The 30-inch rule only governs whether an intermediate landing is needed partway up a run — even a single-run ramp with no intermediate landing still needs a compliant landing at each end.
Related calculators
Frequently asked questions
What is the maximum slope for a wheelchair ramp?
The ADA Standards for Accessible Design set a maximum running slope of 1:12, meaning 1 inch of rise for every 12 inches of ramp length, for any ramp rising more than a small amount. A gentler slope is always allowed and often preferred.
How long does a wheelchair ramp need to be?
At the 1:12 maximum, a ramp needs 12 inches of length for every 1 inch of rise. A ramp climbing 24 inches needs a minimum of 24 feet of ramp length, before accounting for any landings.
Do ramps need landings?
Yes. The ADA requires a level landing at least as wide as the ramp and 60 inches long at the top and bottom of every ramp run, and after every 30 inches of rise within a single run, so long ramps break into shorter runs connected by landings.
What is the maximum rise for a single ramp run?
The ADA limits a single ramp run to a maximum rise of 30 inches before a landing is required. This calculator splits taller total rises into multiple runs at that limit and adds a landing between each.
Sources & references
This tool uses standard formulas and reference values from:
- • American Concrete Institute — ACI 318, Building Code Requirements for Structural Concrete. concrete.org
- • ICC — International Residential Code (IRC), span, footing and framing tables. codes.iccsafe.org
- • APA – The Engineered Wood Association, allowable span and load guidance.
Estimates for planning only. Span, load and code values vary by jurisdiction — verify against your local adopted code and a licensed engineer before building.