By Zencalcy Editorial TeamLast reviewed About us
A ramp converts a vertical rise into a gentle slope. The ADA standard for a ramp used by wheelchair users is 1:12 — one inch of rise for every twelve inches of run, or 8.33% — and that ratio is the starting point for every accessible entrance.
Ramp run and slope from the rise, to ADA ratios.
run (ft) = rise (in) × ratio ÷ 12 slope % = 100 ÷ ratio
The ADA requires a level landing at least 36 inches long wherever the ramp changes direction, at the top and bottom, and after 30 inches of rise. Curbs or edge protection are also required on both sides.
| Symbol | Meaning |
|---|---|
| rise | Total rise to climb, in inches. |
| ratio | Slope as 1 in ratio; 12 is ADA maximum. |
| run | Horizontal length of the ramp. |
24 × 12 ÷ 12 = 24 feet of run at 8.33% slope — the ADA maximum gradient for an accessible ramp.
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A maximum of 1:12, or 8.33%, for ramps used by people with disabilities. Steeper 1:8 ramps are allowed only for short rises in existing structures.
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Content updated: September 2026