Twenty-eight inches: one run, with little to spare
One ramp run may climb 30 inches, so a 28 inch rise still fits in a single 28 ft run with 2 inches to spare. That makes the measurement matter: if the real height from the ground to the door sill is over 30 inches, the ramp needs a second run and a 5 ft landing between the two.
A straight 28 ft ramp needs 38 ft with the top landing and the clear space at the bottom. A landing part way up is not required at this height, but adding one gives a place to rest and lets the ramp turn, at the cost of 5 ft more platform. At 1:16 the ramp is 37.33 ft and still one run, because the limit is on the rise, not the length.
28 inch rise at each slope
| Slope | Ramp length (run) | Along the surface | Percent | Angle | Runs | Footprint with landings |
|---|---|---|---|---|---|---|
| 1:12 (ADA maximum) | 28 ft | 28.10 ft | 8.3% | 4.8° | 1 | 33 ft |
| 1:16 | 37.33 ft | 37.41 ft | 6.3% | 3.6° | 1 | 42.33 ft |
| 1:20 | 46.67 ft | 46.72 ft | 5.0% | 2.9° | 1 | 51.67 ft |
The footprint adds a 5 ft landing at the top. Allow 5 ft of clear, level space at the bottom too: with it the 1:12 ramp needs 38 ft from end to end. That bottom space is not in the concrete estimate below.
Is my ramp too steep for 28 inches?
Slope is rise ÷ run. For a 28 inch rise, a ramp shorter than 28 ft is steeper than 1:12:
| Ramp length | Slope | Percent | Angle | Within 1:12? |
|---|---|---|---|---|
| 24 ft | 1:10.3 | 9.7% | 5.6° | No, 4 ft too short |
| 26 ft | 1:11.1 | 9.0% | 5.1° | No, 2 ft too short |
| 28 ft | 1:12 | 8.3% | 4.8° | Yes |
| 32 ft | 1:13.7 | 7.3% | 4.2° | Yes |
Materials for the 28 ft ramp
A wood ramp 28 ft long and 36 inches wide takes 60 rows of 5/4×6 deck boards laid across it, 198 lineal feet with 10% extra, on 4 joists per run at 16 inch centers (124 lineal feet). The 4 inch concrete for the top landing is 0.34 cubic yards, about 16 bags of 80 lb mix. Built 48 inches wide, the decking rises to 264 lineal feet on the same 4 joists per run. Handrails on both sides, with a 12 inch level extension at the top and bottom of the run, come to 61 lineal feet of rail. Posts, brackets and footings are not in these figures.
Ramp length for nearby rises
| Rise | 1:12 | 1:16 | 1:20 | Runs | Footprint at 1:12 |
|---|---|---|---|---|---|
| 22 in | 22 ft | 29.33 ft | 36.67 ft | 1 | 27 ft |
| 24 in | 24 ft | 32 ft | 40 ft | 1 | 29 ft |
| 28 in | 28 ft | 37.33 ft | 46.67 ft | 1 | 33 ft |
| 30 in | 30 ft | 40 ft | 50 ft | 1 | 35 ft |
| 36 in | 36 ft | 48 ft | 60 ft | 2 | 46 ft |
Coming down steps instead of a measured height? See a ramp for 3 steps or a ramp for 4 steps, or read the ramp length and slope guide.
Want to change anything else? The calculator above is the full Wheelchair Ramp Calculator: edit any number and the results update instantly.
Tools & materials for this project
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Frequently asked questions
How long does a wheelchair ramp need to be for a 28 inch rise?
28 ft at the 1:12 maximum slope, because every inch of rise needs 12 inches of ramp. With the landings it takes up 33 ft. At 1:16 the ramp is 37.33 ft and at 1:20 it is 46.67 ft.
Does a 28 inch rise need a landing in the middle of the ramp?
No. The rise is under the 30 inches one run may climb, so the ramp can be one 28 ft run with a landing at the top. Handrails are needed on both sides: 61 lineal feet with the extensions.
What is the slope of a 28 ft ramp with a 28 inch rise?
1:12, which is 8.3% or 4.8 degrees. Divide the rise by the run in the same unit: 28 ÷ 336 inches = 0.0833.
Related sizes and guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.