Ramp Calculator: design faster, build safer ramps in minutes
Use this Ramp Calculator to size accessible ramps the right way. Enter a rise or select a target ratio, then read off the run, ramp length, grade, and slope angle. The tool follows widely cited accessibility guidance—like the 1:12 maximum running slope in the 2010 ADA Standards for Accessible Design—so you can plan a ramp that’s comfortable, code-aware, and space-efficient.
How to use the Ramp Calculator
You don’t need advanced math. Follow these simple steps and you’ll get a complete ramp layout in seconds.
- Pick an application or enter a ratio. For public access, many designers use 1:12 as a maximum running slope per the ADA Standards §405.2 (8.33% grade). For gentler ramps choose 1:16 or 1:20. Always check local code.
- Enter the total rise. That’s the vertical distance from the lower surface to the upper surface.
- Choose a ramp type. Straight runs are simple. Dog-legs turn 90°. Switchbacks turn 180° with a landing between flights.
- Review read-only results. The calculator shows slope angle (degrees), grade (%), the horizontal run, and the sloped ramp length.
- Refine units. Toggle metric or imperial in any dropdown. Conversions update instantly.
- Save space smartly. If your run exceeds available room, split it into two or more flights with landings. See the landing notes below.
Source for the 1:12 maximum running slope: U.S. Access Board, Chapter 4 – Accessible Routes (§405.2).
Key ramp terms (rise, run, slope, grade)
- Rise: vertical height your ramp must climb.
- Run: horizontal distance from start to end of a single flight.
- Ramp length: the sloped distance along the surface (hypotenuse).
- Slope angle (θ): the angle above level:
θ = arctan(rise/run). - Grade: slope as a percentage:
grade = 100 × rise/run. - Ratio (rise:run): expressed as “1:12”, meaning 1 unit of rise for 12 units of run.
The math behind ramp sizing
Ramp geometry is clean trigonometry. The calculator applies the following formulas under the hood.
| Quantity | Formula | Notes |
|---|---|---|
| Run (from ratio) | run = rise × runPerRise where 1:12 → runPerRise = 12 |
Example: 0.9 m rise at 1:12 → run = 10.8 m |
| Ramp length | length = √(rise² + run²) |
Hypotenuse of a right triangle |
| Grade (%) | grade = 100 × rise / run |
1:12 ≈ 8.333% |
| Slope angle (deg) | θ = arctan(rise/run) × 180/π |
1:12 ≈ 4.76° |
ADA defines a “ramp” as any accessible route steeper than 1:20 (1991 Standards). Ramps serving accessible routes must not be steeper than 1:12 for new work (2010 Standards).
Common ramp presets and what they mean
Our Ramp Calculator ships with sensible presets. They reflect max slopes found in federal accessibility guidance, plus gentler comfort targets used in real projects. Always confirm the governing code in your jurisdiction.
| Preset | Rise:Run | Approx. grade | Approx. angle | Typical use |
|---|---|---|---|---|
| Unassisted user, ADA max slope | 1:12 | 8.33% | ≈ 4.76° | Public routes, new construction maximum |
| ADA “comfortable” target | 1:16 | 6.25% | ≈ 3.58° | Gentler slope for easier self-propulsion |
| ADA “minimum” steepness | 1:20 | 5% | ≈ 2.86° | At or below this, many routes aren’t classified as ramps |
| Assisted residential (short, supervised) | 1:6 (2:12) | 16.67% | ≈ 9.46° | Short moves with caregiver assistance (confirm locally) |
ADA also limits the rise of any single ramp run to 30 inches, and requires landings at the top and bottom of each flight (ADA ). Cross slope should not exceed 1:48 (≈2.08%) (R407.3).
Straight, dog-leg, and switchback layouts
Straight runs
Straight runs are easy to build. They need enough horizontal space for the full run plus landing length at both ends.
90° dog-leg (L-shaped)
When space runs out in one direction, a dog-leg turns the run at a landing. The landing should be at least as wide as the ramp and at least 60 inches long in many public contexts. Check your code before detailing the handrails and guards.
180° switchback (U-shaped)
Switchbacks halve the footprint. You place a flat landing between flights then reverse direction. The landing must allow a wheelchair to turn without encroaching on a sloped surface. Clear space and railing offsets matter here.
- One run’s rise ≤ 30 inches. If the total rise exceeds 30 inches then split into multiple runs.
- Provide landings at every run transition. Landings must be level and at least as wide as the ramp.
- Keep cross slope low. 1:48 maximum keeps wheels from drifting.
Worked examples
Example 1: 0.9 m rise on a public route at 1:12
- Given: rise = 0.9 m; ratio = 1:12
- Run: 0.9 × 12 = 10.8 m
- Length: √(0.9² + 10.8²) ≈ 10.84 m
- Grade: 100 × 0.9 / 10.8 = 8.33%
- Slope angle: arctan(0.9/10.8) = ≈ 4.76°
Example 2: same rise, but target a gentler 1:16
- Run: 0.9 × 16 = 14.4 m
- Angle: arctan(0.9/14.4) = ≈ 3.58°
- Takeaway: The gentler ramp adds length, but many users find it meaningfully easier to climb.
Example 3: total rise 1.2 m with switchback splits
A single 1:12 run would need 14.4 m of horizontal space. If the site only allows 8 m in one direction, split the 1.2 m rise into two runs at 0.6 m each:
- Each run: 0.6 × 12 = 7.2 m
- Landing: insert a 1.5 m (60 in) long level landing between runs (check code for minimums).
- Total footprint: roughly 7.2 m × 2 runs + landing.
Quick rules of thumb
- Use the gentlest slope you can fit. Users notice the difference.
- Keep a single run below 30 inches of rise. Split long climbs into multiple runs with landings.
- Mind cross slope. Aim for 1:48 or flatter.
- Width matters. Many public ramps require at least 36 inches clear width (Access Board guidance).
- Handrails and edges. If required, detail handrails and edge protection per your code family.
Accessibility & safety checklist
Run through this list before you finalize drawings.
- Confirm your governing standard and any local amendments.
- Verify the rise for each run does not exceed the allowed maximum.
- Provide landings at top and bottom of each flight.
- Check clear widths, turning space at landings, and door swing conflicts.
- Keep cross slope low to avoid drift and shoulder strain.
- Specify slip-resistant surface finishes that work when wet.
- Detail edge protection where drop-offs exist.
- Add handrails if required and lay out returns cleanly to avoid snags.
- Coordinate lighting, tactile warnings, and signage where mandated.
Ramp Calculator: frequently asked questions
What’s the difference between slope, grade, and ratio?
They all describe the same geometry in different ways. Ratio expresses rise to run (1:12). Grade uses a percent (8.33%). Slope angle uses degrees (≈4.76°). Convert between them with the formulas above.
Is 1:12 always acceptable?
1:12 is the maximum running slope for many public ramps in the 2010 ADA Standards. Projects outside that scope can have different limits. Existing buildings can use steeper slopes in certain constrained cases per the Standards’ table for existing conditions. Always confirm with your authority having jurisdiction.
How long can a ramp be?
The ADA Standards limit the rise of any single run, not the total length. Very long systems can be fatiguing so designers often split them into shorter runs with landing areas for rest.
Do I measure run along the slope?
No. Run is horizontal. Ramp length is the sloped distance.
Are residential ramps different?
Many residential projects still follow the 1:12 idea for comfort and safety though enforcement varies. Some assisted-use ramps are steeper for short distances. Work with your local building department for an official answer.
What about curb ramps?
Curb ramps follow related but specific requirements. Access Board materials summarize those rules and note the 1:12 maximum for the running slope of the curb ramp surface, plus a 1:48 maximum cross slope.
A good Ramp Calculator saves time yet the design choice still rests with you. Start with a clear rise, set a humane target slope, then check landings and clearance. If you need to turn, use a dog-leg or switchback. Keep surfaces slip-resistant and cross slopes low. Confirm the details with the standard that governs your project. Do this and your ramp will feel natural to navigate, not just technically compliant.
