Ramp Calculator
Enter the rise to climb and your slope ratio to get the ramp's run, slope length, angle — and how many landings the rise forces.
Last updated: 2026-09-28
How the calculation works
- Run multiplies the rise by the slope ratio: every inch of rise costs 12 inches of run at 1:12.
- Slope length is the hypotenuse — the actual board or concrete length along the incline.
- Landing count follows the ADA 30-inch-rise-per-run cap, with level landings between runs.
Formula
run = rise × slope_ratio slope_angle = atan(1/X)
| Symbol | Meaning | Unit |
|---|---|---|
rise | Vertical height to overcome | in |
run | Horizontal ramp length | ft |
Worked example
Interpreting the result
The 1:12 limit is why ramps eat space: a 30 in rise demands 30 ft of run before landings — swamped porches switch to switchback configurations with an intermediate landing. 1:20 (5%) avoids handrail and grip requirements entirely, which sometimes makes a longer, gentler ramp the cheaper compliant build. Always verify against your local accessibility code — ADA is the US federal baseline, and jurisdictions add their own.
Assumptions
- Straight run; switchbacks add landing length between runs.
- ADA reference values (US federal); local codes may differ.
Limitations
- Handrail, width (36 in clear) and landing dimensions are referenced, not designed.
- Not for vehicle ramps (different slope conventions entirely).
Frequently asked questions
What is the ADA maximum ramp slope?
1:12 (8.33%, 4.76°) for ramps, with 30 in maximum rise per run and level landings between. At 1:20 or gentler, the surface is a 'walk' without handrail requirements.
How long should a wheelchair ramp be for 3 steps?
Three 7 in steps = 21 in rise → 21 ft of run at 1:12. Plan the landings: 60 in level at top and bottom minimum.