# What ADA ramp slope and length?

ADA ramp slope calculator: the ramp length, runs and landings for a rise at the ADA’s 1:12 maximum slope, or a check of whether your ramp meets it.

- Page: https://www.acalculator.org/construction/ada-ramp-calculator
- JSON spec: https://www.acalculator.org/construction/ada-ramp-calculator.json
- Version: a4acbc98c5ca

## Default answer

Example with the default inputs (Find Ramp length, Rise 24 in, Slope 1:12 (ADA maximum), Most rise per run 30 in, Landing length 60 in): The ramp takes 24 ft 0 in in all: 24 ft 0 in of slope at 1:12 (meets the ADA 1:12 limit), plus no landing between.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| find | Find | Find the ramp length for a slope, or check the slope of a ramp you have measured. |
| rise | Rise | The height from the lower level to the top: ground to door threshold. |
| s | Slope | Inches of ramp length for each inch of rise. The ADA allows 1:12 at most. |
| k | Slope ratio, 1 : | Units of ramp length for each unit of rise, such as 14 for 1:14. |
| run | Ramp run | The level distance the sloped part covers, landings left out. |
| mr | Most rise per run | The most rise one sloped run may have before a landing. ADA: 30 in. |
| ld | Landing length | The length of each level landing between runs. ADA: at least 60 in. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| total | Length in all | The sloped runs plus the landings between them, measured level. |
| runLength | Sloped length, measured level | Rise × the slope ratio: the level distance of all the runs. |
| sloped | Length along the slope | √(rise² + run²): the length of the ramp surface. |
| withEnds | With top and bottom landings | Length in all + one landing at the top and one at the bottom. |
| ratioText | Slope ratio | 1 : (run ÷ rise). |
| percent | Slope, percent | Rise ÷ run × 100. |
| angle | Slope angle | The arctangent of rise ÷ run, in degrees. |
| runs | Sloped runs | Rise ÷ most rise per run, rounded up. |
| landings | Landings between runs | Sloped runs − 1. |
| ada | ADA slope check | Whether the slope is 1:12 or flatter (ADA 405.2). |
| landingText | Landings | The landings between runs, in words. |

## Method

Run = rise × slope ratio (1:12 by default), or ratio = run ÷ rise; runs = rise ÷ most rise per run (30 in by default), rounded up; length in all = run + (runs − 1) × landing (60 in by default); a ramp meets ADA 405.2 when run ÷ rise ≥ 12.

## Assumptions

- ADA 405.2: slope not steeper than 1:12; 405.6: one run rises at most 30 in; 405.7.3: landings at least 60 in long.
- Lengths are measured level (plan view), as the ADA measures slope.

## Worked examples

1. find = length, rise = 0.762, s = 12, mr = 0.762, ld = 1.524 gives runLength = 9.144, runs = 1, total = 9.144, withEnds = 12.192. Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03).
2. find = length, rise = 1.8288, s = 12, mr = 0.762, ld = 1.524 gives runLength = 21.9456, runs = 3, landings = 2, total = 24.9936, landingText = 2 landings between. Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03).
3. find = slope, rise = 0.4572, run = 4.572, mr = 0.762, ld = 1.524 gives ratioText = 1:10, ada = steeper than the ADA 1:12 limit, percent = 10. Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03).

## FAQ

### What is the ADA ramp slope?

ADA 405.2 says a ramp run may not be steeper than 1:12: one unit of rise for every 12 units of level run, a grade of 8.33% or 4.76°.

### How do I calculate ADA ramp length?

Multiply the rise in inches by 12 to get the ramp run in inches, or read the rise in inches as the run in feet. A 30 in rise needs 30 ft of ramp.

### What is the maximum rise for an ADA ramp run?

30 in (ADA 405.6). A higher rise is split into runs with a level landing between each pair.

### How long must an ADA ramp landing be?

At least 60 in long in the direction of travel (405.7.3), and at least as wide as the ramp run (405.7.2). A landing is needed at the top and bottom of every run.

### How long is an ADA ramp for a 72 in rise?

72 ft of sloped ramp, split into 3 runs (72 ÷ 30, rounded up) with 2 landings of 5 ft between them: 82 ft, or 92 ft with the top and bottom landings.

### Does my ramp meet ADA?

Divide the level run by the rise. If the result is 12 or more the slope meets 405.2. A ramp rising 18 in over 15 ft (180 in) is 1:10, too steep.

## Sources

- US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps: 405.2 slope not steeper than 1:12; 405.5 clear width at least 36 in; 405.6 rise of a run at most 30 in; 405.7.2 and 405.7.3 landings as wide as the run and at least 60 in long, retrieved 2026-10-03. https://www.access-board.gov/ada/#ada-405
- NIST Special Publication 811 (2008), Appendix B: 1 in = 0.0254 m and 1 ft = 0.3048 m exactly, retrieved 2026-10-03. https://www.nist.gov/pml/special-publication-811