# Wheelchair ramp slope: how long?

Wheelchair ramp slope calculator: the ramp length for a rise at 1:12, 1:16, 1:20 or any slope, or the slope of a ramp you measured, with the runs, landings, percent grade and angle.

- Page: https://www.acalculator.org/construction/wheelchair-ramp-calculator
- JSON spec: https://www.acalculator.org/construction/wheelchair-ramp-calculator.json
- Version: ca4bf8153bf2

## 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 (or ratio = run ÷ rise); runs = rise ÷ most rise per run, rounded up; length in all = run + (runs − 1) × landing.

## Assumptions

- ADA 405.2: a ramp slope may not be steeper than 1:12; 405.6: one run rises at most 30 in; 405.7.3: landings are at least 60 in long.
- The ramp is straight; a turn at a landing changes the footprint but not the lengths.
- Lengths are measured level (plan view), as the ADA measures slope.

## Worked examples

1. find = length, rise = 0.6096, s = 12, mr = 0.762, ld = 1.524 gives runLength = 7.3152, total = 7.3152, runs = 1, ratioText = 1:12, ada = meets the ADA 1:12 limit. 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 = 0.9144, s = 12, mr = 0.762, ld = 1.524 gives runLength = 10.9728, runs = 2, landings = 1, total = 12.4968, withEnds = 15.5448. 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 = 0.508, run = 6.096, mr = 0.762, ld = 1.524 gives ratioText = 1:12, percent = 8.333333, angle = 4.763642. 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).
4. find = slope, rise = 0.762, run = 7.62, mr = 0.762, ld = 1.524 gives ratioText = 1:10, percent = 10, ada = steeper than the ADA 1:12 limit. 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).
5. find = length, rise = 0.5, s = 20, mr = 0.75, ld = 1.5 gives runLength = 10, sloped = 10.012492, runs = 1. 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 slope for a wheelchair ramp?

The ADA Standards allow a ramp slope no steeper than 1:12: 1 in of rise for every 12 in of run, a grade of 8.33% or about 4.76°. A gentler 1:16 or 1:20 is easier to push up.

### How long does a wheelchair ramp need to be?

Multiply the rise by the slope ratio. At 1:12, each inch of rise needs 12 in (1 ft) of ramp, so a 24 in rise needs a 24 ft ramp.

### When does a ramp need a landing?

Under ADA 405.6 one run may rise at most 30 in. A higher rise is split into runs with a level landing between them, at least 60 in long (405.7.3), and there is a landing at the top and the bottom too.

### How long is a ramp for a 36 in rise?

At 1:12 the sloped part is 36 ft. 36 in is more than 30 in, so it takes two runs with a 5 ft landing between them: 41 ft in all, or 51 ft with top and bottom landings.

### How do I check the slope of my ramp?

Measure the rise and the level run, then divide the run by the rise. A ramp rising 20 in over 20 ft (240 in) is 240 ÷ 20 = 12, a 1:12 slope.

### How wide must a wheelchair ramp be?

ADA 405.5 asks for a clear width of at least 36 in between handrails, and landings at least as wide as the ramp.

## 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