Wheelchair Ramp Calculator
| Rise | Run at 1:12 | Run at 2:12 | Run at 1:20 |
|---|---|---|---|
| 12 in (1 step) | 12 ft | 6 ft | 20 ft |
| 24 in (porch) | 24 ft | 12 ft | 40 ft |
| 30 in (ADA cap) | 30 ft | 15 ft | 50 ft |
| 48 in (high entry) | 48 ft, 2 runs | 24 ft, 2 runs | 80 ft |
| ADA rule | Number |
|---|---|
| Max rise per run | 30 inches |
| Landings, top / bottom / between runs | 60 inches long, level |
| Clear width between rails | 36 inches minimum |
| Handrail height | 34-38 inches |
| Cross slope (drainage) | 1:48 maximum |
Ramp sizing is one division problem people get badly wrong by eyeballing it: for every inch of rise, the ADA-standard 1:12 slope asks twelve inches of run, so a routine 24-inch porch - two steps plus a threshold - demands a 24-foot ramp before any landing is counted. That ratio is not bureaucratic fussiness; it is the slope a person can self-propel up in a manual chair and descend without braking fear, and it is the number every manufacturer, contractor and code official will check your build against.
Bottom line: measure the total rise in inches, then multiply by the slope factor - 12 for 1:12, 16 for 1:16, 20 for 1:20 - to get run in inches, divide by 12 for feet. Any rise over 30 inches cannot be a single straight run at all: the ADA caps one run at 30 inches of rise and requires a flat 60-inch landing between runs, which is where L-shaped and switchback layouts come from. The calculator returns the run, how many runs and landings your rise implies, and the layout verdict.
The honest part: 1:12 is the standard for public accommodations and the right default for a home user who may weaken over the years. A short residential ramp at 2:12 is buildable and common when the yard refuses to give up 24 feet - but it is a workout for a manual chair, unsafe in ice, and wrong for anyone who does not push themselves. The alternatives that actually save space are longer run in a switchback, a porch lift for rises past about 5 feet, or re-grading the entry; the table below shows the whole trade so the decision is arithmetic, not hope.
How to use
- Measure rise, not steps: from the landing surface down to the ground at the ramp's start - the calculator wants inches. Two 7-inch steps plus a 1.5-inch threshold is a 15.5-inch rise, and 15.5, not 2, is the number that sizes the ramp.
- Pick the slope honestly: 1:12 for anyone who may self-propel, 2:12 only for short rises pushed by a strong companion, 1:16 to 1:20 when the user has limited upper-body strength or a heavy power chair that needs the gentlest grade.
- Read the runs-and-landings verdict before buying lumber: past 30 inches of rise the ramp needs flat 60-inch landings between runs and level 60-inch platforms at top and bottom, and that footprint - not the ramp run - is what usually decides between a straight, L-shaped or switchback layout.
Frequently asked questions
What slope should a wheelchair ramp be?
The ADA standard is 1:12 - one inch of rise per twelve inches of run, about 8.3 percent, roughly 4.8 degrees. It is the maximum slope permitted for a wheelchair ramp in the ADA standards for public accommodations, and the sensible home default. Anything steeper trades the user's independence for your lumber budget, so make that trade deliberately: 2:12 for a short rise with a strong assistant, never for a self-propelling user's only entrance.
How long a ramp do I need for 3 steps?
Three steps at the typical 7-inch riser is about 21 inches of rise, plus any threshold. At 1:12 that is 21 feet of run - call it 24 feet with the bottom approach - and because 21 inches is under the 30-inch single-run cap, one straight run with a 60-inch platform at top and bottom works. The calculator turns your actual measured rise into the exact number rather than the step-count guess, because riser heights vary more than people expect.
Can a home ramp be steeper than 1:12?
Legally, private homes are usually not bound by the ADA at all - residential codes vary, and 2:12 is a common builder shortcut for rises under about 12 inches. The tradeoffs are physical, not legal: 2:12 doubles the effort per foot, stops many manual-chair users outright, and turns icy or wet. If the ramp is the only way in, build 1:12; if it is the backup entrance, 2:12 with a handrail edge is an honest compromise.
What are the landing and switchback rules?
Every ramp needs a level 60-inch-long platform at the top and bottom, and any run that rises more than 30 inches must be split into multiple runs with a 60-inch flat landing between them. Ramps wider than one run or longer than about 30 feet also want a resting landing. Switchbacks need a 60-inch-by-60-inch platform at the turn. These platforms are not comfort extras - they are where a person rests mid-climb and where a wheelchair actually fits while opening the door.
How wide and how strong should a ramp be?
36 inches is the ADA minimum clear width between handrails or edge protection - build 42 to 48 inches in practice so hands, bags and a companion fit. Strength matters more than people expect: the deck must carry the chair plus companion, commonly 300 to 500 pounds concentrated mid-span, which is why 2-by-6 framing at 16-inch centers and 4-by-4 posts on footings is the usual floor, not 2-by-4 vanity framing.
Do I need a permit for a home wheelchair ramp?
Often yes - ramps over 30 inches high usually need footings and a building permit even on private homes, and requirements vary by city and county, so a two-minute call to the local building department beats a redo order. If you are modifying a rental or condo, add the landlord or HOA to the call. Funding help exists in several programs for veterans and seniors, and an inspector who approves the plan early is also an ally when a contractor quote looks wrong.