ADA Ramp Slope Calculator
Design a wheelchair ramp to US accessibility code (ADA Standards §405). Enter the total rise to get the required ramp length, running slope, and the landings you need — checked against the 1:12 maximum slope and 36″ minimum width, with a downloadable PDF report.
| Check | Your value | Requirement | Status |
|---|---|---|---|
| Enter your ramp to run the checks | |||
| Slope | Grade | Required run | Footprint |
|---|---|---|---|
| Enter a rise to compare slopes | |||
How to use the ADA ramp slope calculator
Four quick steps turn your total rise into the required ramp length, the running slope for the space you have, and the landings you need — checked against ADA §405, with a downloadable report.
Enter rise & run
Give the total rise in inches and the horizontal run you have in feet, plus the ramp width.
Pick a design slope
Choose 1:12 (ADA max), 1:16, or 1:20 — gentler slopes are easier to use but need more length.
Set the use
Public/commercial must meet ADA; residential ramps use the same slope for safety.
Read results & save a PDF
See the required length, running slope, landings, and a pass/fail on each ADA check — then download a report.
How the ramp is calculated
Required length comes from the rise and your design slope; the actual running slope comes from the run you have; and landings are added for every 30″ of rise. Here is the exact math the calculator runs.
Worked example — 24″ rise, 30 ft available run, 36″ wide, 1:12 design
Required run at 1:12: 24 × 12 / 12 = 24 ft
Actual slope at 30 ft: 1 : (30 × 12 / 24) = 1:15 (6.67%) — gentler than the max ✓
Runs: ceil(24 / 30) = 1 · Landings: 1 + 1 = 2 (5 ft each)
Footprint: 30 + 2 × 5 = 40 ft · Width 36″ ✓
✓ Meets ADA — slope 1:15, needs 24 ft at max (you have 30). Handrails required (rise > 6″).
ADA ramp reference charts
Handy lookups for the ADA §405 limits, ramp length by rise and slope, and what the three slope choices mean. Confirm handrails and local rules with your building department.
| Requirement | Limit | Note |
|---|---|---|
| Max running slope | 1:12 (8.33%) | Steepest allowed |
| Max cross slope | 1:48 (2.08%) | Side to side |
| Min clear width | 36″ | Between handrails |
| Max rise per run | 30″ | Then a landing |
| Landing length | ≥ 60″ (5 ft) | Top, bottom & between runs |
| Handrails | if rise > 6″ | Both sides |
All measured on the finished ramp. This tool checks slope, length, width, and landings — not handrail or edge-protection details.
| Total rise | Ramp run | Runs | Landings |
|---|---|---|---|
| 6″ | 6 ft | 1 | 2 |
| 12″ | 12 ft | 1 | 2 |
| 24″ | 24 ft | 1 | 2 |
| 30″ | 30 ft | 1 | 2 |
| 36″ | 36 ft | 2 | 3 |
| 48″ | 48 ft | 2 | 3 |
1 ft of ramp per inch of rise at 1:12. A single run maxes at 30″ of rise, so taller ramps need more runs and landings.
| Slope | Grade | Run per inch of rise |
|---|---|---|
| 1:12 | 8.33% | 1.0 ft — ADA maximum |
| 1:16 | 6.25% | 1.33 ft — easier to use |
| 1:20 | 5.00% | 1.67 ft — gentlest, no handrails |
Gentler slopes are safer and easier to self-propel, at the cost of a longer ramp. Build gentler than 1:12 whenever you have the room.
Everything the calculator works out
A rise and a run give you the required ramp length, the actual slope, the landings, and a pass/fail on every ADA check — so you can plan a usable ramp before you build.
Key figures behind the ramp
Built for an accessible, usable ramp
From a home ramp for a family member to a commercial accessibility upgrade, the same calculator turns a rise into a compliant design.
Building a ramp for a wheelchair or walker user and wants it gentle enough to use safely every day.
- Enter the porch rise
- Choose a gentle slope
- Plan landings & handrails
Making an entrance accessible and needs the ramp to meet ADA for a public building.
- Set use to public
- Confirm slope & width pass
- Add required handrails
Wants to know if a rise fits the available run, or how much footprint a compliant ramp needs.
- Enter rise & available run
- Compare slopes & footprints
- Attach the PDF to the set
7 things to know about ADA ramps
A ramp is only useful if it’s actually usable, so slope and landings matter as much as passing code. These points keep it safe and compliant.
ADA ramp slope calculator FAQ
The slope, length, and accessibility questions people ask most when planning a ramp.
The ADA (§405) sets a maximum running slope of 1:12 — one inch of rise per 12 inches of run, about 8.33% or 4.76°.
That’s the steepest allowed, not the target. Where you have room, a gentler 1:16 or 1:20 is easier and safer, especially for someone self-propelling. A 1:20 (5%) surface isn’t technically a ramp and needs no handrails.
The cross slope — side to side — is separately limited to 1:48 (about 2%).
At the ADA maximum 1:12, you need 1 foot of ramp per inch of rise.
A 24″ rise needs a 24-foot run at 1:12; a gentler 1:16 needs 32 feet and 1:20 needs 40. Landings add to the total footprint on top of the ramp run.
The formula: required run (ft) = rise (in) × ramp ratio ÷ 12. Divide rise by 12 and multiply by the ratio for the length before landings.
Running slope is rise ÷ run, as a ratio like 1:12. Divide the run by the rise (same units) for the second number.
A 24″ rise over a 24-foot (288″) run is 288 ÷ 24 = 12, or 1:12 — right at the max. The same rise over only 20 feet is 240 ÷ 24 = 10, a 1:10 slope, too steep and failing ADA.
As a percent, slope is rise ÷ run × 100; 1:12 ≈ 8.33%. The bigger the second number, the gentler the ramp.
Yes. The ADA requires a level landing at the top and bottom of every ramp, and an intermediate landing wherever a single run rises more than 30 inches.
Landings must be at least as wide as the ramp and a minimum of 60 inches (5 ft) long, so a person can rest and maneuver. Where the ramp changes direction, the landing must be big enough to turn (typically 60 × 60).
Because one run tops out at 30″ of rise, a tall ramp is a series of runs joined by landings — which add significantly to the footprint.
Under the ADA, ramps with a rise greater than 6 inches require handrails on both sides. A very gentle 1:20 surface isn’t a ramp and doesn’t require them, but any true ramp of meaningful height does.
Handrails must be continuous, 34–38″ above the surface, graspable, with extensions at top and bottom. Ramps also need edge protection — a curb, barrier, or extended surface — to keep a wheel from rolling off.
This calculator focuses on slope, length, width, and landings; confirm handrail and edge details with your building department.
The ADA requires a minimum clear width of 36 inches between the handrails. That’s clear space, so the overall ramp is wider once you add handrails and any curb.
Thirty-six inches is the floor; wider is friendlier where two people pass or someone uses a larger power chair. Some occupancies and local codes require more for higher-traffic ramps.
Keep the 36″ clear width consistent along the whole run and across landings, and confirm any wider requirement locally.
It can be. The 1:12 maximum is the legal limit but it’s demanding — climbing an 8.33% grade under your own power in a manual wheelchair takes real strength and can be unsafe for many people.
That’s why the ADA and advocates recommend building gentler where there’s space: 1:16 or 1:20 is markedly easier. The trade-off is length — a gentler slope needs more ramp and landings — but for a daily-use ramp it’s usually worth it.
If the ramp serves a specific person, match the slope to what they can comfortably manage, not just the code minimum.
The ADA legally applies to public and commercial buildings, not private single-family homes. But its slope, width, and landing rules are the recognized standard for a safe, usable ramp, so most residential ramps are built to them anyway.
Building to ADA — or gentler — means the ramp will actually work for the person who needs it. Local codes may still require a permit and set their own residential accessibility provisions, and some programs or insurers require ADA compliance.
Public or private, check with your building department before building; a permit is commonly required either way.
Estimate only — not a substitute for a plan review. This calculator checks ramp slope, length, width, and landings against the ADA Standards §405 model limits (max running slope 1:12, min clear width 36″, a landing at the top, bottom, and every 30″ of rise), in inches and feet. It does not check handrails, handrail extensions, edge protection, cross slope, landing sizes at turns, surface, drainage, or structural design, all of which are required for a compliant, safe ramp — and local jurisdictions may amend these rules. Accessibility is a life-safety matter: confirm the complete design with your local building department and permit set, and where a ramp serves a specific person, build to what they can safely use. For planning purposes only.