How long does a ramp need to be for a 24 inch rise?
At the ADA's 1:12, a 24" rise needs 24 ft of ramp — a foot of run for every inch of rise — plus a landing at each end. Ramp lengths for every rise, and where a run has to stop for a landing.
A 24" rise needs 24 ft of ramp at the ADA maximum slope of 1:12.
With a 60" landing at the top and the bottom, the whole thing is 34 ft end to end, at a slope of 4.76°.
How that is worked out
- 1:12 means 12" of run for every inch of rise, so 24" × 12 = 288" — 24 ft. In other words, one foot of ramp per inch of rise.
- No single run may rise more than 30", so 24" fits in 1 run. A 48" rise would be 2 runs with 1 landing between.
- Every run has a landing at least 60" long at its top and bottom: 24 ft of slope plus two landings is 34 ft.
Ramp length by rise, with 60" landings
| Rise | Run at 1:12 | Runs | End to end, landings in | Run at 1:20 |
|---|---|---|---|---|
| 6" | 6 ft | 1 | 16 ft | 10 ft |
| 12" | 12 ft | 1 | 22 ft | 20 ft |
| 18" | 18 ft | 1 | 28 ft | 30 ft |
| 24" | 24 ft | 1 | 34 ft | 40 ft |
| 30" | 30 ft | 1 | 40 ft | 50 ft |
| 36" | 36 ft | 2 | 51 ft | 60 ft |
| 48" | 48 ft | 2 | 63 ft | 80 ft |
Worth knowing
- These are the 2010 ADA Standards' limits, and they are defaults, not law, for a house. The ADA governs public accommodations; a ramp at a private home is usually governed by the local residential code, if anything — ring the building department before you build.
- 1:12 is the steepest the Standards allow, not a comfortable slope. Somebody pushing their own wheelchair finds 1:20 far easier, at the cost of a ramp 1.67 times as long.
- Any run rising more than 6" needs handrails on both sides, and the clear width between them is at least 36".
- A ramp that will not fit straight can switch back on itself, but the turning landing then needs 60" × 60", not just 60" long.
Sources: 2010 ADA Standards for Accessible Design, US Department of Justice.
Work out your own numbers
- Wheelchair ramp
Ramp length from the rise at 1:12 or gentler, with the runs, landings and handrails, checked against the ADA Standards.
- Stair handrail
Rail length and angle for a straight flight, the plumb and level cuts, and the IRC height, grip and guard checks.
- Stair stringers
Divide the rise into even risers, lay out the notches, and check the result against the code.
Related questions
- How long should a wheelchair ramp be?
- One foot for every inch of rise at the ADA maximum of 1:12 — so 24 ft for a 24" rise — plus a 60" landing at each end. A gentler 1:20 is easier to climb and needs 40 ft for the same rise.
- What angle is a 1:12 ramp?
- 4.76°, or a grade of 8.3%. It sounds shallow, and it is the steepest slope the ADA Standards allow for a new ramp.
- When does a ramp need a landing in the middle?
- When it rises more than 30". No single run may climb further than that, so a taller rise is split into equal runs with a landing at least 60" long between each.