Enter the height the ramp has to climb and the slope. The calculator gives the horizontal run, the length along the ramp, the angle and how many runs and landings you need under the ADA limits.
ADA ramp rules used here
The U.S. Access Board’s guide to the ADA Standards limits the running slope of a ramp to 1:12, meaning 12 in of run for every inch of rise, and limits the rise of each run to 30 in. A ramp that climbs more than 30 in needs a level landing between runs.
Ramp formula
Run (in) = rise (in) × slope ratio Length along the ramp = √(rise² + run²) Runs = rise ÷ 30 in, rounded up Intermediate landings = runs − 1
Worked example: 24 in rise at 1:12
- Run: 24 × 12 = 288 in = 24 ft.
- Length along the ramp: 24.08 ft.
- Rise is under 30 in, so one run with landings at the top and bottom only.
Ramp length by rise (1:12)
| Rise | Run | Runs | Intermediate landings |
|---|---|---|---|
| 6 in | 6 ft | 1 | 0 |
| 12 in | 12 ft | 1 | 0 |
| 18 in | 18 ft | 1 | 0 |
| 24 in | 24 ft | 1 | 0 |
| 30 in | 30 ft | 1 | 0 |
| 36 in | 36 ft | 2 | 1 |
| 48 in | 48 ft | 2 | 1 |
Landings add length too. The ADA Standards set minimum landing sizes, handrail rules and edge protection; a home ramp may follow different local rules. A gentler 1:16 or 1:20 slope is easier for many people to use, at the cost of a longer ramp.
Questions
How long does a ramp need to be for 3 steps?
Three 7 in steps are a 21 in rise, so 21 ft of run at 1:12.
What is the maximum ramp slope?
1:12 under the ADA Standards, with no more than 30 in of rise per run.
Do residential ramps have to meet ADA?
Not always; private homes are often covered by local codes instead. 1:12 is still a widely used guide.
Sources
- Chapter 4: Ramps and Curb Ramps, U.S. Access Board.
Used for: Maximum running slope of 1:12 and a 30 in maximum rise per run.