acalculator

What ADA ramp slope and length?

Type the rise from the ground to the door. The ADA ramp slope calculator gives the ramp length at the 1:12 maximum slope, the runs and landings the ADA Standards ask for, or checks whether a ramp you measured meets 1:12.

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

ADA ramp slope calculator: the ramp length, runs and landings for a rise at the ADA’s 1:12 maximum slope, or a check of whether your ramp meets it.

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 (1:12 by default), or ratio = run ÷ rise; runs = rise ÷ most rise per run (30 in by default), rounded up; length in all = run + (runs − 1) × landing (60 in by default); a ramp meets ADA 405.2 when run ÷ rise ≥ 12.

  • ADA 405.2: slope not steeper than 1:12; 405.6: one run rises at most 30 in; 405.7.3: landings at least 60 in long.
  • 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 30 in, Slope 1:12 (ADA maximum), Most rise per run 30 in, Landing length 60 in gives Sloped length, measured level 30 ft 0 in, Sloped runs 1, Length in all 30 ft 0 in, With top and bottom landings 40 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)
  2. Find Ramp length, Rise 72 in, Slope 1:12 (ADA maximum), Most rise per run 30 in, Landing length 60 in gives Sloped length, measured level 72 ft 0 in, Sloped runs 3, Landings between runs 2, Length in all 82 ft 0 in, Landings 2 landings between.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 18 in, Ramp run 15 ft, Most rise per run 30 in, Landing length 60 in gives Slope ratio 1:10, ADA slope check steeper than the ADA 1:12 limit, Slope, percent 10.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

This is the wheelchair ramp calculator set to the ADA limits: slope 1:12 (ADA 405.2), at most 30 in of rise per run (405.6), and 60 in landings (405.7.3). You can change any of them.

Find the ramp length. With slope ratio k (12 here, or 16, 20 or a number you type):

  • 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, rounded up; landings between runs = runs − 1.
  • Length in all = run + landings between runs × landing length.
  • 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".

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. Typed lengths are read back as exact decimals, so the ratio, the run count and the 1:12 check are exact.

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 30 in rise. Run = 30 × 12 = 360 in = 30 ft. One run, no landing between: 30 ft; with top and bottom landings, 30 + 2 × 5 = 40 ft.

A 72 in rise. Run = 72 × 12 = 864 in = 72 ft. 72 ÷ 30 = 2.4, so 3 runs and 2 landings: 72 + 2 × 5 = 82 ft.

A ramp rising 18 in over 15 ft. 180 ÷ 18 = 10: a 1:10 slope, 10%, steeper than the 1:12 limit.

Other questions people ask

What is the ADA ramp slope?

ADA 405.2 says a ramp run may not be steeper than 1:12: one unit of rise for every 12 units of level run, a grade of 8.33% or 4.76°.

How do I calculate ADA ramp length?

Multiply the rise in inches by 12 to get the ramp run in inches, or read the rise in inches as the run in feet. A 30 in rise needs 30 ft of ramp.

What is the maximum rise for an ADA ramp run?

30 in (ADA 405.6). A higher rise is split into runs with a level landing between each pair.

How long must an ADA ramp landing be?

At least 60 in long in the direction of travel (405.7.3), and at least as wide as the ramp run (405.7.2). A landing is needed at the top and bottom of every run.

How long is an ADA ramp for a 72 in rise?

72 ft of sloped ramp, split into 3 runs (72 ÷ 30, rounded up) with 2 landings of 5 ft between them: 82 ft, or 92 ft with the top and bottom landings.

Does my ramp meet ADA?

Divide the level run by the rise. If the result is 12 or more the slope meets 405.2. A ramp rising 18 in over 15 ft (180 in) is 1:10, too steep.