About the Wheelchair Ramp Calculator
This wheelchair ramp calculator turns the height you need to climb — the rise from ground to door threshold or porch — into the ramp length required for a chosen slope. It uses the ADA maximum running slope of 1:12 (one inch of rise per foot of run) by default, and lets you pick gentler 1:16 or 1:20 slopes that are easier for manual wheelchair users.
Because the 2010 ADA Standards limit any single ramp run to 30 inches of rise, taller rises are split into several runs with level landings between them. The calculator counts the runs, the landings (top, bottom and intermediate, each at least 60 inches long) and the total straight-line footprint so you can see whether the ramp fits your yard or needs switchbacks.
Use it for home accessibility projects, planning a rental or modular ramp, or checking a contractor’s layout. Residential ramps are not always legally bound by ADA, but its rules are the widely used benchmark for safe, usable ramps.
With the default inputs, the ramp length (horizontal run) is 24 ft. Change any value above to recalculate instantly.
How to use the wheelchair ramp calculator
- 1Measure the vertical rise from the ground to the top of the threshold or porch.
- 2Choose a slope — 1:12 is the ADA maximum; 1:16 or 1:20 are easier to climb.
- 3Read the ramp length and how many runs and landings you need.
- 4Check the footprint against your space and plan switchbacks if needed.
- 5Add handrails for any run rising more than 6 inches.
Formula and method
A 1:12 slope means every inch of rise needs 12 inches of horizontal run, so the ramp length in feet equals the rise in inches for 1:12 (and 1.33× or 1.67× that for 1:16 and 1:20). Slope percent is 100 ÷ ratio and the angle is arctan(1 ÷ ratio) — about 4.76° at 1:12.
The 2010 ADA Standards (405.6) cap each ramp run at 30 inches of rise, so the rise is divided by 30 and rounded up to find the number of runs. Level landings at least 60 inches long are required at the top and bottom of every run (405.7), which gives runs + 1 landings; the footprint assumes a straight layout.
- rise
- Total vertical height (in)
- ratio
- Horizontal inches per inch of rise (12 for 1:12)
- 30 in
- Maximum rise per run under ADA 405.6
- 5 ft
- Minimum landing length (60 in)
Worked examples
24 in porch at the ADA 1:12 slope
At 1:12, 24 inches of rise needs 24 feet of run. Since it is under 30 inches, one run is enough, with a 5 ft landing at the top and bottom — a 34 ft straight footprint.
36 in rise needs two runs
36 inches of rise at 1:12 is 36 ft of ramp. That exceeds the 30-inch limit per run, so it is split into two 18 ft runs with an intermediate landing — three landings and 51 ft in a straight line.
18 in rise at a gentle 1:20
A 1:20 slope needs 20 inches of run per inch of rise: 18 × 20 = 360 in = 30 ft. The 5% slope (2.86°) is much easier for self-propelled wheelchair users.
Frequently asked questions
What is the ADA slope for a wheelchair ramp?+
The maximum running slope is 1:12 — 1 inch of rise per 12 inches (1 foot) of run, or 8.33%. Gentler slopes such as 1:16 or 1:20 are easier for manual wheelchair users when space allows.
How long does a ramp need to be for 3 steps?+
Three typical 7-inch steps give about a 21-inch rise, which needs a 21 ft ramp at 1:12, plus a 5 ft landing at the top and bottom — about 31 ft in a straight line.
How often does a ramp need a landing?+
Under the 2010 ADA Standards a single run may rise no more than 30 inches, so a landing at least 60 inches long is needed after every 30 inches of rise, plus landings at the top and bottom.
When does a ramp need handrails?+
ADA requires handrails on both sides of a ramp run when the rise is greater than 6 inches. Handrail tops go 34–38 inches above the ramp surface.
How wide should a wheelchair ramp be?+
The ADA minimum clear width between handrails is 36 inches. Many residential builders make ramps 42–48 inches wide for easier maneuvering and helper access.
Results are general estimates and not legal advice. Laws vary by jurisdiction — consult a qualified attorney.