acalculator

Wheelchair ramp slope: how long?

Type the rise from the ground to the door and pick a slope, or type the length of a ramp you have. The wheelchair ramp slope calculator gives the ramp length, the runs and landings the ADA rules call for, the percent grade and the angle.

Your numbers

Units
Find
Length in all
24 ft 0 in

The ramp takes 24 ft 0 in in all: 24 ft 0 in of slope at 1:12 (meets the ADA 1:12 limit), plus no landing between.

Sloped length, measured level
24 ft 0 in
Length along the slope
24 ft 1 in
With top and bottom landings
34 ft 0 in
Slope ratio
1:12
Slope, percent%
8.33
Slope angle°
4.76
Sloped runs
1
Landings between runs
0
ADA slope check
meets the ADA 1:12 limit
Landings
no landing between

Length in all: 24 ft 0 in. The ramp takes 24 ft 0 in in all: 24 ft 0 in of slope at 1:12 (meets the ADA 1:12 limit), plus no landing between.

How to calculate

Wheelchair ramp slope calculator: the ramp length for a rise at 1:12, 1:16, 1:20 or any slope, or the slope of a ramp you measured, with the runs, landings, percent grade and angle.

Example with the default inputs (Find Ramp length, Rise 24 in, Slope 1:12 (ADA maximum), Most rise per run 30 in, Landing length 60 in): The ramp takes 24 ft 0 in in all: 24 ft 0 in of slope at 1:12 (meets the ADA 1:12 limit), plus no landing between.

Method: Run = rise × slope ratio (or ratio = run ÷ rise); runs = rise ÷ most rise per run, rounded up; length in all = run + (runs − 1) × landing.

  • ADA 405.2: a ramp slope may not be steeper than 1:12; 405.6: one run rises at most 30 in; 405.7.3: landings are at least 60 in long.
  • The ramp is straight; a turn at a landing changes the footprint but not the lengths.
  • Lengths are measured level (plan view), as the ADA measures slope.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Find Ramp length, Rise 24 in, Slope 1:12 (ADA maximum), Most rise per run 30 in, Landing length 60 in gives Sloped length, measured level 24 ft 0 in, Length in all 24 ft 0 in, Sloped runs 1, Slope ratio 1:12, ADA slope check meets the ADA 1:12 limit.Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03)
  2. Find Ramp length, Rise 36 in, Slope 1:12 (ADA maximum), Most rise per run 30 in, Landing length 60 in gives Sloped length, measured level 36 ft 0 in, Sloped runs 2, Landings between runs 1, Length in all 41 ft 0 in, With top and bottom landings 51 ft 0 in.Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03)
  3. Find Slope of my ramp, Rise 20 in, Ramp run 20 ft, Most rise per run 30 in, Landing length 60 in gives Slope ratio 1:12, Slope, percent 8.333333, Slope angle 4.763642.Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03)
  4. Find Slope of my ramp, Rise 30 in, Ramp run 25 ft, Most rise per run 30 in, Landing length 60 in gives Slope ratio 1:10, Slope, percent 10, ADA slope check steeper than the ADA 1:12 limit.Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03)
  5. Find Ramp length, Rise 19.69 in, Slope 1:20, Most rise per run 29.53 in, Landing length 59.06 in gives Sloped length, measured level 32 ft 9.7 in, Length along the slope 32 ft 10.2 in, Sloped runs 1.Source: US Access Board, ADA Accessibility Standards, Chapter 4, 405 Ramps (405.2 slope not steeper than 1:12; 405.6 rise of a run at most 30 in; 405.7.3 landings at least 60 in long), https://www.access-board.gov/ada/#ada-405 (retrieved 2026-10-03)

How it works

Find the ramp length. The slope ratio k is 12, 16, 20, or a number you type (1:k means k units of run for each unit of rise).

  • Sloped length, measured level (run) = rise × k.

Check the slope of my ramp. Type the level run of the sloped part, without landings.

  • Slope ratio k = run ÷ rise, shown as 1:k with k rounded half up to 2 decimals.

Then, in both modes:

  • Sloped runs = rise ÷ most rise per run (30 in by default, ADA 405.6), rounded up.
  • Landings between runs = sloped runs − 1.
  • Length in all = run + landings between runs × landing length (60 in by default, ADA 405.7.3).
  • With top and bottom landings = length in all + 2 × landing length.
  • Length along the slope = √(rise² + run²).
  • Slope, percent = rise ÷ run × 100; slope angle = arctan(rise ÷ run) in degrees.
  • ADA slope check: "meets the ADA 1:12 limit" when k ≥ 12, otherwise "steeper than the ADA 1:12 limit" (ADA 405.2).

Rules

  • Rise and most rise per run are from 1 mm to 10 m; the run from 1 mm to 1 km; the landing from 1 mm to 100 m; a typed ratio from 1 to 1,000.
  • A rise and run so far apart that the ratio or the percent leaves the floating-point range has no answer.

Output format

Lengths show in feet and inches to 0.1 in (US) or in metres (Metric); percent and angle to 2 decimals; the ratio as 1:k. Rise, run and landing are read back as the exact decimals you typed, so the ratio, the run count and the ADA check are exact; the sloped length and the angle use a square root and an arctangent.

The answer reads: "The ramp takes [length in all] in all: [sloped length] of slope at [ratio] ([ADA check]), plus [no landing between | 1 landing between | n landings between]."

Worked examples by hand

A 24 in rise at 1:12. Run = 24 × 12 = 288 in = 24 ft. 24 in ≤ 30 in, so one run and no landing between: 24 ft in all, 34 ft with top and bottom landings.

A 36 in rise at 1:12. Run = 36 × 12 = 432 in = 36 ft. 36 ÷ 30 = 1.2, so 2 runs and 1 landing: 36 + 5 = 41 ft; with top and bottom landings, 51 ft.

A ramp rising 20 in over 20 ft. 240 ÷ 20 = 12, a 1:12 slope; 20 ÷ 240 × 100 = 8.33%; arctan(1/12) = 4.76°. It meets the 1:12 limit.

A ramp rising 30 in over 25 ft. 300 ÷ 30 = 10, a 1:10 slope (10%), steeper than the 1:12 limit.

A 0.5 m rise at 1:20. Run = 10 m; along the slope √(0.5² + 10²) = 10.0125 m.

Other questions people ask

What is the slope for a wheelchair ramp?

The ADA Standards allow a ramp slope no steeper than 1:12: 1 in of rise for every 12 in of run, a grade of 8.33% or about 4.76°. A gentler 1:16 or 1:20 is easier to push up.

How long does a wheelchair ramp need to be?

Multiply the rise by the slope ratio. At 1:12, each inch of rise needs 12 in (1 ft) of ramp, so a 24 in rise needs a 24 ft ramp.

When does a ramp need a landing?

Under ADA 405.6 one run may rise at most 30 in. A higher rise is split into runs with a level landing between them, at least 60 in long (405.7.3), and there is a landing at the top and the bottom too.

How long is a ramp for a 36 in rise?

At 1:12 the sloped part is 36 ft. 36 in is more than 30 in, so it takes two runs with a 5 ft landing between them: 41 ft in all, or 51 ft with top and bottom landings.

How do I check the slope of my ramp?

Measure the rise and the level run, then divide the run by the rise. A ramp rising 20 in over 20 ft (240 in) is 240 ÷ 20 = 12, a 1:12 slope.

How wide must a wheelchair ramp be?

ADA 405.5 asks for a clear width of at least 36 in between handrails, and landings at least as wide as the ramp.