Ramp Calculator
At the ADA maximum slope of 1:12, every inch of rise needs a foot of ramp run, and a single run may rise no more than 30 in before a level landing. A 24 in rise needs 24 ft of run and 24.08 ft of sloped surface, plus top and bottom landings. For steps instead, use the Stair Calculator.
How it's calculated: Run = rise × slope ratio; sloped length = √(rise² + run²); intermediate landings = ⌈rise ÷ max rise per run⌉ − 1; handrail = sides × (sloped length + landing lengths).
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Run = rise × slope ratio n (1:12 → run = 12 × rise)
Sloped length = √(rise² + run²)
Ramp runs = ⌈ rise ÷ max rise per run ⌉; intermediate landings = runs − 1
Handrail = sides × (sloped length + landing lengths)
Run the calculation to see each step with your own numbers.
24 in rise, 1:12 slope, handrails both sides, 30-in max rise per run.
Run = 2 ft × 12 = 24 ft
Sloped length = √(2² + 24²) = 24.08 ft
Runs = ⌈24 in ÷ 30 in⌉ = 1 → 0 intermediate landings; footprint ≈ 24 ft + top/bottom landings
Handrail = 2 × 24.08 = 48.2 ft
- Straight ramp. A switchback or dogleg adds a 60-in × 60-in turning landing at each turn — add those to the footprint.
- Slope ratio is the running slope. ADA/IBC: 1:12 maximum for new work, 1:16–1:20 preferred; cross slope ≤ 1:48; each run rises ≤ 30 in; landings ≥ 60 in long and at least as wide as the ramp.
- This sizes the ramp geometry — it does not check local code adoption, occupancy, edge protection, or loading. Confirm with your building department.
- Top and bottom landings are required but not added to the footprint figure — add 5 ft at each end.
- How long does a wheelchair ramp need to be?
- At the ADA maximum of 1:12, you need 1 foot of ramp run for every inch of rise — so a 24-inch porch needs 24 feet of ramp, plus level landings top and bottom. Gentler slopes (1:16–1:20) are longer but much easier to use, especially for someone self-propelling.
- What slope ratio should I use?
- 1:12 is the steepest allowed for new construction. 1:16 to 1:20 is much easier to self-propel and is worth the extra length wherever you have room for it.
- How much space does a switchback ramp need?
- Each turn adds a 60 in by 60 in turning landing. A tall rise done as a switchback fits in a much smaller footprint than a straight run, but you add a landing at every direction change.
- When does a ramp need a landing?
- Under the 2010 ADA Standards, a single ramp run may rise at most 30 in, and every run needs a level landing at its top and bottom, at least 60 in long. Where the ramp changes direction, the landing must be at least 60 × 60 in.
- Does a ramp need handrails?
- Under the 2010 ADA Standards, ramp runs that rise more than 6 in need handrails on both sides. The handrails must also extend 12 in beyond the top and bottom of each run; the handrail length here does not include those extensions.
- How long is a ramp for a 30-inch rise?
- At 1:12, a 30 in rise needs 30 ft of horizontal run and about 30.1 ft of sloped surface. It fits in a single run with no intermediate landing, and handrails on both sides total about 60.2 ft, before the top and bottom landings.
Ramp geometry
Run = rise × slope ratio; sloped length = √(rise² + run²). Standard geometry.
Slope & landing limits
2010 ADA Standards §405 (running slope ≤ 1:12, rise ≤ 30 in per run, landings ≥ 60 in) and IBC §1012. Referenced for the limits shown; confirm the code edition your jurisdiction enforces.
Slope & landing limits — reference
About the Ramp Calculator
The Ramp Calculator turns a total rise and a slope ratio into the horizontal run, the sloped surface length to build, the number of intermediate landings, and the handrail length. It applies the common accessibility limits — a 1:12 maximum running slope for new work, and a level landing after every 30 in of rise — but it sizes geometry only and does not check which code edition your jurisdiction enforces. Top and bottom landings are required but not added to the footprint figure.
What you enter
- Total rise (ground to threshold)
- Slope ratio (1 : n) — The 'n' in 1:n. ADA maximum is 1:12 for new construction; 1:16 to 1:20 is easier to use.
- Handrails
- Max rise per ramp run before a landing — ADA: a single ramp run may rise at most 30 in before a level landing.
What you get back
- Horizontal run (total) — the exact result of the calculation.
- Sloped surface length (total) — The actual length of ramp surface to build (hypotenuse). Slightly longer than the run.
- Intermediate landings — Plus a level landing at the top and bottom (not counted here). Each landing ≥ 60 in long.
- Total footprint length (ramp + landings) — Run plus 5 ft per intermediate landing. Add top/bottom landings and any switchback turns.
- Handrail length — the exact result of the calculation.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Stair Calculator — Stair rise, run, stringer length and step count for a total height.
- Concrete Calculator — How much concrete a rectangular slab or footing needs, in cubic yards or cubic metres.
- Decking Calculator — Decking boards, joists and fasteners for a deck of a given size.
Part of the Accessibility calculators.