Wheelchair Ramp Calculator
Calculate ramp length, landings, and ADA compliance from your rise and slope ratio. Sizes accessible ramps at the 1:12 standard for doorways and porches.
How this calculator works
Ramp length is set by the rise and the slope ratio you choose. The calculator converts rise into run at that ratio, counts the landings the rise requires, and checks the result against the ADA 1:12 standard.
Formula: Ramp length (ft) = (rise in × slope ratio) ÷ 12. Intermediate landings = ⌈rise ÷ 30⌉ − 1. ADA compliant when ratio ≥ 12.
Worked example
A 24-inch rise at a 1:12 slope:
- Ramp length: (24 × 12) ÷ 12 = 24 ft
- Landings needed: ⌈24 ÷ 30⌉ − 1 = 0 intermediate landings (top and bottom landings still required)
- ADA: 12 ≥ 12 → compliant
Slope reference
| Rise | Length at 1:12 | Length at 2:12 |
|---|---|---|
| 12 in | 12 ft | 6 ft |
| 24 in | 24 ft | 12 ft |
| 36 in | 36 ft | 18 ft |
How to measure
Measure the vertical rise from the lower grade to the top landing or threshold. Choose 1:12 for accessible public use. Long ramps usually fold into switchbacks — add a level landing wherever the ramp turns or every 30 inches of rise.
Frequently asked questions
What slope does ADA require for a ramp?
The ADA maximum is 1:12 — one inch of ramp length for every inch of rise, a 4.8 percent grade. Gentler is better for comfort; steeper than 1:12 is not compliant for public accessibility. This calculator flags whether your ratio meets the standard.
When do I need a landing?
The ADA requires a level landing at the top and bottom of every ramp, and an intermediate landing for each 30 inches of vertical rise. The calculator counts the intermediate landings your rise requires; each landing is at least 60 inches long.
How long will my ramp be?
At 1:12, ramp run in inches equals rise in inches times 12. A 24-inch rise needs a 24-foot run — accessible ramps get long fast, which is why switchbacks with landings are common where space is tight.
Can I build a steeper ramp for my own home?
For private, non-public use you can, and portable ramps sometimes use 2:12 or 3:12 for occupancy. But steeper ramps are harder and less safe to use, especially unassisted — stay as close to 1:12 as your space allows.
Does the ramp length include landings?
No — the length shown is the sloped run only. Add the length of each landing (60 inches minimum) plus turning space to get the total footprint the ramp will occupy.
Estimates only. Verify quantities with your supplier before purchasing.