The maximum slope for a wheelchair ramp under the ADA is 1:12: 1 inch of rise for every 12 inches of run, an 8.33% grade or about 4.8 degrees. So every inch a ramp climbs needs a foot of ramp, and a 24 in porch needs 24 ft of slope plus landings. This page has a ramp length calculator, a chart of ramp lengths by rise, and the full list of ADA ramp requirements with their section numbers.
Ramp length calculator
Ramp length by rise
| Rise | Run at 1:12 | Run at 1:16 | Run at 1:20 | Runs (30 in max rise each) | Length at 1:12 with 60 in landings | Handrails required |
|---|---|---|---|---|---|---|
| 3 in | 3.0 ft | 4.0 ft | 5.0 ft | 1 | 13.0 ft | no |
| 6 in | 6.0 ft | 8.0 ft | 10.0 ft | 1 | 16.0 ft | no |
| 8 in | 8.0 ft | 10.7 ft | 13.3 ft | 1 | 18.0 ft | yes |
| 12 in | 12.0 ft | 16.0 ft | 20.0 ft | 1 | 22.0 ft | yes |
| 18 in | 18.0 ft | 24.0 ft | 30.0 ft | 1 | 28.0 ft | yes |
| 24 in | 24.0 ft | 32.0 ft | 40.0 ft | 1 | 34.0 ft | yes |
| 30 in | 30.0 ft | 40.0 ft | 50.0 ft | 1 | 40.0 ft | yes |
| 36 in | 36.0 ft | 48.0 ft | 60.0 ft | 2 | 51.0 ft | yes |
| 42 in | 42.0 ft | 56.0 ft | 70.0 ft | 2 | 57.0 ft | yes |
| 48 in | 48.0 ft | 64.0 ft | 80.0 ft | 2 | 63.0 ft | yes |
| 60 in | 60.0 ft | 80.0 ft | 100.0 ft | 2 | 75.0 ft | yes |
Ramp slope in ratio, percent and degrees
| Ratio | Percent grade | Angle | Status |
|---|---|---|---|
| 1:20 | 5.0% | 2.86° | The steepest walking surface that is not a ramp (definition 106.5, 403.3) |
| 1:16 | 6.25% | 3.58° | Gentler than required; easier for manual wheelchairs |
| 1:12 | 8.33% | 4.76° | Maximum for new ramps (405.2) |
| 1:10 | 10% | 5.71° | Existing sites only, rise 6 in max (Table 405.2) |
| 1:8 | 12.5% | 7.13° | Existing sites only, rise 3 in max; steeper is prohibited |
ADA ramp requirements
| Item | Requirement | 2010 ADA Standards |
|---|---|---|
| Running slope | 1:12 maximum (8.33%) | 405.2 |
| Cross slope | 1:48 maximum (about 2%) | 405.3 |
| Rise per run | 30 in maximum, then a landing | 405.6 |
| Clear width | 36 in minimum, measured between handrails where provided | 405.5 |
| Landings | Top and bottom of every run; as wide as the ramp; 60 in long minimum; 60 x 60 in where the ramp turns | 405.7 |
| Handrails | Both sides when a run rises more than 6 in; top of gripping surface 34 to 38 in; 1-1/4 to 2 in round; 1-1/2 in from the wall; extend 12 in level beyond top and bottom | 405.8, 505.4, 505.5, 505.7, 505.10.1 |
| Edge protection | A curb or barrier that stops a 4 in sphere within 4 in of the surface, or the surface extended 12 in beyond the handrail | 405.9 |
| Surface | Stable, firm and slip resistant; no changes in level on the run | 405.4, 302 |
| Wet conditions | Landings designed so water does not collect | 405.10 |
The 2010 ADA Standards apply to public accommodations, commercial facilities and state and local government buildings. Private single-family homes are not covered, but these dimensions are the usual reference for accessible homes and renovations; multifamily housing may fall under the Fair Housing Act design rules instead, and local building codes add their own. For a house, the International Residential Code (section R311.8) has its own ramp rules, which your building department will apply; check them before you build.
Building a ramp: practical notes
- Measure the rise from the ground at the end of the ramp, not from the ground at the door; on sloping ground the run can be shorter or longer than the chart.
- A switchback or L-shaped ramp with 60 x 60 in turning landings fits a long ramp into a small yard.
- Gentler is better if you have the room: 1:16 or 1:20 is far easier for someone pushing their own chair or for a helper pushing.
- Wood ramps outdoors need ground-contact treated posts, decking spaced for drainage and a slip-resistant surface.
- Portable and modular ramps are rated by their makers for a maximum rise; check the rating rather than the length alone.
Frequently asked questions
What is the ADA ramp slope?
1:12 maximum, an 8.33% slope or about 4.8 degrees: 1 in of rise per 12 in of run (2010 ADA Standards 405.2).
How long does a wheelchair ramp need to be?
1 ft of ramp for every inch of rise at 1:12, plus landings. A 24 in rise needs 24 ft of slope; with 60 in landings at top and bottom, about 34 ft overall.
How often does a ramp need a landing?
At the top and bottom of every run, and every 30 in of rise at most; a 1:12 run therefore needs a landing at least every 30 ft (405.6, 405.7).
Does a ramp need handrails?
Yes, on both sides, when a run rises more than 6 in (405.8).
How wide does an ADA ramp have to be?
36 in clear minimum, measured between the handrails (405.5).
Sources
- US Department of Justice, 2010 ADA Standards for Accessible Design, sections as cited (text read 24 October 2026). Federal regulation, public domain.
Last reviewed: 24 October 2026. Numbers in the tables are our arithmetic from the sources listed; code sections are summarised, not quoted. How we check our work: methodology and corrections. Spotted an error? Please let us know.