Ramp Calculator
Work out wheelchair ramp length, slope, runs and landings from the rise and check them against ADA 2010 Section 405 or the IRC, or use any custom slope.
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About this toolWhat is the Ramp Calculator?
A wheelchair ramp is mostly a length problem. The ADA 2010 Standards for Accessible Design allow a running slope of no more than 1:12, so every inch of rise needs a foot of horizontal run, and a single run may climb no more than 30 inches before it needs a level landing. This ramp calculator turns the rise into the horizontal run, the sloped length, the number of runs and landings and the total footprint, then lists the code checks that apply.
Choose ADA for new public construction, the ADA existing-site exceptions for tight spots with small rises, the residential code (IRC) for a home, or a custom slope for a shed, trailer or loading ramp. Enter the total rise from the ground to the threshold and the clear width, and the result updates as you type.
Each check is shown as a pass or a fail with the section number, so you can see which rule a design breaks and whether a turn with a landing, a longer run or a lower rise would fix it.
- ADA 2010 Section 405, existing-site Table 405.2, IRC R311.8 and custom slopes
- Run, sloped length, angle, percent and number of runs
- Landings and straight footprint, handrail length per side
- Pass or fail checks with section numbers
- Inches or millimetres, copy and share link
How to use the Ramp Calculator
- Choose inches or millimetres.
- Pick the design rule: ADA new construction, ADA existing site, residential IRC, or custom.
- Enter the total rise from the lower walking surface to the top landing or door threshold, and the clear width between handrails.
- For an existing site choose 1:10 or 1:8 if the rise allows; for custom, enter the slope as a ratio, percent or angle and an optional maximum rise per run.
- Read the horizontal run, sloped length, runs, landings and footprint, then work through any failed checks.
Worked examples
Three steps to a front door
Input
ADA, 24 in rise, 36 in wide
Output
24 ft of run (24.08 ft sloped), one run, footprint 34 ft with top and bottom landings
At 1:12 a 24 inch rise needs 288 inches of run. The rise is over 6 inches, so handrails are needed on both sides.
A 48 inch porch
Input
ADA, 48 in rise
Output
Two runs of 24 in rise and 24 ft run, one intermediate landing, 63 ft straight footprint with all landings
The rise is over 30 inches, so the ramp must be split. Most designs turn at the middle landing (60 x 60 in) to fit on a lot.
Truck loading ramp
Input
Custom, 1:6, 36 in rise
Output
18 ft of run, 9.46 degrees
Accessibility rules do not apply here; check the maximum angle in your equipment manual.
Background and insight
The rules come from Section 405 of the 2010 ADA Standards. The running slope may not be steeper than 1:12 (405.2) and the cross slope not steeper than 1:48 (405.3). Clear width between handrails is at least 36 inches (405.5). The rise of any single run is 30 inches at most (405.6). Landings at the top and bottom of every run are at least as wide as the ramp and at least 60 inches long, and a landing where the ramp changes direction is at least 60 by 60 inches (405.7). Runs that rise more than 6 inches need handrails on both sides (405.8), mounted 34 to 38 inches high (505.4) and extending 12 inches beyond the top and bottom of the run (505.10).
Existing sites get limited relief under Table 405.2 when space does not allow 1:12: a slope between 1:12 and 1:10 is allowed for a rise of 6 inches at most, and between 1:10 and 1:8 for a rise of 3 inches at most. Nothing steeper than 1:8 is permitted.
Homes follow the International Residential Code where adopted. IRC R311.8 sets a maximum ramp slope of 1:12, allowing 1:8 only where 1:12 is technically infeasible, requires 36 by 36 inch landings at the top and bottom, at doors and at turns, and requires a handrail on at least one side of ramps steeper than 1:12. Many people still build home ramps to ADA dimensions because they are easier to use. Loading ramps for vehicles and equipment are outside these rules; follow the equipment maker's maximum angle.
Common use cases
Home access
Size a ramp for a wheelchair user before buying a modular kit or lumber.
Small businesses
Check an entrance ramp against ADA 405 before a contractor quote or an accessibility review.
Thresholds and small changes in level
Use the existing-site table for short ramps of a few inches where space is tight.
Sheds, trailers and loading docks
Work out the length for a mower, cart or hand truck at any slope.
Tips and limitations
- Measure the rise with a level and a tape from the ground where the ramp will start, not from the nearest step.
- A turn at a landing (L or U shape) often fits a long ramp onto a small lot.
- Add edge protection, such as a curb or rail, where the side of the ramp drops off (ADA 405.9).
- Use a slip-resistant surface and keep water from pooling on landings.
- Local codes and permits may add rules; this calculator is a design aid, not an approval.
Frequently asked questions
How long does a wheelchair ramp need to be?
At the ADA maximum slope of 1:12, one foot of horizontal run for every inch of rise. A 24 inch rise needs a 24 foot run, plus 60 inch landings at the top and bottom.
What is the maximum ADA ramp slope?
1:12, which is 8.33% or about 4.76 degrees (ADA 405.2). Existing sites may use up to 1:10 for a rise of 6 inches or less and up to 1:8 for a rise of 3 inches or less (Table 405.2).
When does an ADA ramp need a landing?
At the top and bottom of every run, and wherever a run has risen 30 inches (405.6). Landings are at least 60 inches long and as wide as the ramp, and 60 by 60 inches where the ramp turns (405.7).
When are handrails required on a ramp?
Under the ADA, on both sides of any ramp run that rises more than 6 inches (405.8), at 34 to 38 inches high. The IRC requires a handrail on at least one side of residential ramps steeper than 1:12.
How wide does an ADA ramp have to be?
At least 36 inches clear between handrails (405.5). Wider ramps are easier for scooters and for people walking beside a wheelchair.
Do home wheelchair ramps have to meet ADA rules?
Private homes are generally covered by the residential code, not the ADA. The IRC allows 1:12 slopes with 36 inch landings. Building to ADA dimensions is still a good idea for comfort and resale.
Is there an in-depth guide to the Ramp Calculator?
Yes. “ADA Ramp Rules: Slope, Rise, Landings and Handrails” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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