One inch of rise, one foot of ramp — and the landings nobody plans for
ADA Ramp Calculator
Enter the total rise you need to overcome and this calculator returns the ramp length at your chosen slope, how many runs and landings the code requires, where the handrails are triggered, and the full footprint — so you know before you draw whether the ramp fits the site. Switch between commercial (ADA) and residential (IRC) rules and every check updates.
How Ramp Length Is Calculated
Length follows directly from slope. At the ADA maximum of 1:12, one inch of rise needs one foot of ramp — a clean, memorable ratio. A 30-inch rise, the most a single run may climb, needs 30 feet of ramp. Choose a gentler 1:16 or 1:20 for comfort and the run grows proportionally.
Then the landings. This is where ramps outgrow their sites. A level landing at least 60 inches long is required at the top, at the bottom, and every time the run reaches 30 inches of rise. A landing where the ramp changes direction must be 60 by 60 inches. Add them up and a tall entry ramp becomes a switchback that eats a surprising amount of ground — which is exactly why you want the number before you commit the plan.
Handrails and edges. Any ADA run rising more than 6 inches needs handrails on both sides, 34 to 38 inches above the surface, plus edge protection so a wheel cannot roll off. Keep at least 36 inches clear between the rails.
ADA vs. Residential Requirements
| Requirement | ADA — commercial | IRC — residential |
|---|
| Max running slope | 1:12 (8.33%) | 1:12 (1:8 if space-limited) |
| Max cross slope | 1:48 | — |
| Max rise per run | 30″ | No set limit |
| Landing length | 60″ min (60×60 at turns) | ≥ ramp width (36″ min) |
| Handrails | Both sides if rise > 6″ | ≥1 side if steeper than 1:12 |
| Min clear width | 36″ | 36″ |
| Edge protection | Required | Guards where drop > 30″ |
*The 1:8 slope is permitted by the IRC only where site constraints make 1:12 impractical, and is not ADA-accessible. Figures follow the 2010 ADA Standards and 2021 IRC; verify against your local amendments and authority having jurisdiction.
Frequently Asked Questions
What is the maximum slope for an ADA ramp?
1:12 (8.33%) running slope, 1:48 cross slope. At 1:12 a single run may rise no more than 30″ before a landing.
How long does a wheelchair ramp need to be?
At 1:12, one foot of ramp per inch of rise — a 24″ rise needs 24 ft. Gentler 1:16 and 1:20 need more; landings add to the footprint.
When are handrails required?
ADA: both sides on any run rising over 6″, 34–38″ high. IRC: at least one side on ramps steeper than 1:12; guards where the drop exceeds 30″.
What is the maximum rise per run?
30″ for ADA. Above that, break the ramp into runs separated by 60″ landings (60×60″ at a direction change).
ADA vs. residential ramps?
Both aim for 1:12; ADA adds the 30″-per-run limit, 60″ landings, handrails both sides and a 36″ clear width. The IRC allows 1:8 where space is truly limited and sizes landings to the ramp width.
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