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Stairs Calc

Ramp slope

The rise-to-run ratio of an accessible ramp; ADA caps it at 1:12.

Ramp slope is the steepness of a ramp expressed as a ratio of vertical rise to horizontal run, used where stairs are replaced by an incline for wheelchair, stroller, or wheeled access. The ADA caps a new accessible ramp at 1:12 — one inch of rise per twelve inches of run — with a maximum 30 in (762 mm) of rise per ramp run before a level landing is required. Example: a 24 in (610 mm) total rise at 1:12 needs 24 ft (7.3 m) of ramp plus landings top and bottom. Gentler ratios like 1:16 or 1:20 are easier still and may avoid handrails on short rises. Unlike a staircase there are no risers — the run is continuous — but a handrail and edge protection are required once the rise passes 6 in.

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Related terms

Total rise Vertical distance from the lower finished floor to the upper finished floor. Run (going) The horizontal depth of one step, measured nosing-to-nosing, not counting the overhang. Handrail The graspable rail along a stair; code height 34–38 in above the nosing line. Stair angle (pitch) The slope of the flight in degrees; comfortable stairs sit around 30–37°.

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ADA Ramp Calculator Enter your total rise and target slope to get the ramp length, run, number of switchback runs and landings, and clear width — each checked against the ADA §405 accessibility limits.
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Written by the Stairs Calc editorial team. Methodology and code references: see our methodology.

Built and maintained by builders, drafters and engineers who plan stairs for a living — every code limit is transcribed from the published standard and cited to its exact section.

Last reviewed 2026-06-20 against IRC 2021/2024

Stairs Calc gives accurate geometry and checks it against published building-code limits, but results are estimates for planning. Codes are adopted and amended locally and change over time. Always confirm dimensions against your local adopted code and a licensed professional before you build.