Formula and input notes
Horizontal run = rise × slope ratio; sloped length = √(run² + rise²)
| Input | Practical note |
|---|---|
| Slope ratio | Enter horizontal run per one unit of rise. A value of 12 means 12 inches of run for each 1 inch of rise. |
Worked ramp example
Ramp Calculator example: 29.86 in × 12:1 = 358.32 in (29.86 ft) of horizontal run. The sloped length is √(358.32² + 29.86²) = 359.56 in.
Check whether the required run fits
Use the required run to test whether the site can physically accommodate the chosen ratio before preparing a compliant layout.
Landings, accessibility, and structure
Landings, turns, handrails, edge protection, door maneuvering space, drainage, and site slope add dimensions not represented by one straight flight.
Questions specific to this calculation
What does a 12:1 ramp ratio mean?
It means 12 units of horizontal run for each 1 unit of vertical rise. Because both use the same unit, a 30-inch rise at 12:1 requires 360 inches, or 30 feet, of horizontal run before landings.
Does the result establish an accessible ramp design?
No. The tool does not check maximum rise per run, landings, clear width, cross slope, handrails, edge protection, door maneuvering space, drainage, or structural support. Verify the rules that apply to the site and use.