Last updated: August 20, 2026
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Ramp length is the one decision in this category that cannot be made by eye, and it is the one people most often try to make by eye anyway. A ramp that physically reaches the step looks like it works, right up until someone has to push a chair up it, or control it coming down. The slope is what decides that, and slope is a ratio between two numbers you can measure in about two minutes.
This walkthrough covers how to measure the rise correctly, which slope ratio applies to your situation, how to convert that into a length, and the practical checks at the top and bottom that a calculation alone will not catch.
Quick Answer
How do you work out what length ramp you need?
- Measure the total rise: the vertical distance from the lower surface to the top of whatever the ramp lands on, including any lip.
- Apply a slope ratio. The ADA standard specifies a maximum running slope of 1:12, so one foot of ramp per inch of rise, and portable ramp manufacturers publish their own recommended ratios per model.
- Round up to the next available length rather than down. A ramp slightly longer than the calculation is always easier to use.
- Check there is level ground at the bottom and a level landing at the top before ordering.
Bottom line: measure the rise, apply the ratio the manufacturer specifies, round up, and check both ends are level.
Measure the Rise, Not the Steps
The number you need is the total vertical rise, measured from the surface the ramp starts on to the top of the surface it lands on. Hold a tape measure vertically against the face of the steps, or run a level out from the top landing and measure straight down at the far end if the ground slopes away.
Counting steps and multiplying by a typical riser height is where errors creep in, because risers vary and the bottom one is often different from the rest. Measure the whole thing in one go, and include any threshold lip at the top, since that lip is part of what the ramp has to climb.
Which Slope Ratio Applies
Slope is written as a ratio of rise to run. The ADA standard specifies a maximum running slope of 1:12 for ramps in accessible construction, meaning twelve inches of ramp for every inch of rise. That is the gentlest of the commonly used figures and the safest default when you are unsure.
Portable ramp manufacturers publish their own recommended slopes for their products, and those often differ depending on whether the chair is occupied or empty and whether it is manual or powered. Use the figure printed for the model you are buying rather than a general rule, and where the two disagree, the gentler slope is the one to follow.
Who Is Actually Using It Matters
A slope that a strong assistant can push comfortably is not the same as one a person can propel themselves up, and going down is a different problem again, since a steep ramp needs controlling rather than powering. If the user self-propels, plan on the gentlest ratio available. If someone assists, the assistant’s strength and footing on a wet surface are what set the practical limit.
Convert the Rise Into a Length
At 1:12, the arithmetic is as simple as it gets: every inch of rise needs one foot of ramp. A six-inch rise wants six feet, a twelve-inch rise wants twelve feet. Our wheelchair ramp length calculator handles other ratios and awkward numbers.
| Total rise | Length at 1:12 | Typical situation |
|---|---|---|
| 2 inches | 2 feet | Doorsill, usually a threshold wedge instead |
| 6 inches | 6 feet | One step or a curb |
| 12 inches | 12 feet | Two steps |
| 20 inches | 20 feet | Three steps, beyond portable territory |
| 30 inches | 30 feet | The ADA standard limits a single ramp run to 30 inches of rise |
Two things fall out of that table quickly. Small rises are handled better by a threshold ramp than by a long ramp, and once you pass a couple of steps, the length required stops being something anyone wants to carry.
Check the Space Before You Order
A calculation gives a length, not a location. Pace out the run on the ground and confirm the ramp will not finish in a flowerbed, on a slope, at the edge of a driveway, or across a path that people need to walk along.
Check the top too. The ADA standard requires level landings at the top and bottom of each ramp run, and the reason is practical: someone needs somewhere flat to stop, open a door, and manage the transition. A ramp that lands directly against an outward-opening door leaves no room to do any of that.
The Bottom End Needs Level Ground
The lower end of the ramp should meet firm, level ground rather than grass, gravel, or a sloped driveway. A ramp resting on soft ground settles unevenly, which changes the slope and creates a lip at the transition. A paving slab or a firm pad under the bottom edge is a cheap fix and worth doing before it becomes a problem.
Round Up, Not Down
Available lengths come in steps, and calculations rarely land exactly on one. Always go to the next length up. A slightly gentler slope than calculated costs nothing in use, while a slightly steeper one shows up on every single trip, and it shows up most on the days when the surface is wet and the light is poor.
The exception is when the longer ramp will not fit the run available or becomes too heavy to handle. If that happens, it is a signal that the portable route has reached its limit rather than a reason to accept a steep ramp.
Once You Have Your Number
For a rise of one step or a curb, a folding ramp in the calculated length is the usual answer, and the closed dimensions matter as much as the open ones.
For two steps, a longer multi-fold ramp packs shorter for storage while still giving the run the calculation asks for.
And where the rise turns out to be an inch or two rather than a step, a threshold wedge is the simpler and cheaper answer.
When the Answer Is Not a Portable Ramp
If the calculation returns a length you cannot fit, cannot store, or cannot lift, the portable category has run out. At that point a permanent ramp is the appropriate route, and that is a construction project involving local building codes, permits in many jurisdictions, and structural work.
That belongs with a licensed contractor working to your local requirements rather than with a product guide. Knowing where the line sits is genuinely useful, though, because it stops people buying a portable ramp that was never going to work and discovering it after delivery.
A Note on Getting Advice
How steep a slope is manageable depends on the chair, the user, and whether anyone is assisting, and those are exactly the variables a calculation cannot see. If you are unsure what fits your situation, ask your doctor or an occupational therapist, who can watch the actual approach and advise on the slope rather than just the arithmetic.
Frequently Asked Questions
How long should a ramp be for two steps? Measure the rise rather than counting steps, since riser heights vary. Two steps commonly total somewhere around twelve to sixteen inches, which at a 1:12 ratio calls for twelve to sixteen feet of ramp.
What slope should a wheelchair ramp be? The ADA standard specifies a maximum running slope of 1:12 for accessible construction. Portable ramp manufacturers publish their own recommended ratios per model, which can differ by whether the chair is occupied and whether it is manual or powered. Use the figure for your model, and prefer the gentler one.
Is 1:12 the same as an eight percent grade? Roughly, yes. One inch of rise over twelve inches of run works out to about eight and a third percent. Manufacturers and standards more often express it as a ratio, which is easier to work with when measuring.
Does the ramp length include the top plate? Manufacturers usually quote the overall length including the transition plates, but not always. Check the specification, since a few inches at each end matters when a calculation lands close to a size boundary.
What if I do not have room for the calculated length? Then the portable route has reached its limit for that rise. The options are a switchback or permanent ramp designed to local code, or reconsidering which entrance is used, since a side or garage door often has a lower rise.
Is a steeper ramp acceptable if someone is pushing? Manufacturers sometimes publish different ratios for assisted use, and those figures belong to that specific product. Going down a steep ramp is harder to control than going up, so plan for the descent rather than the climb.
How much rise can one ramp run cover? The ADA standard limits a single ramp run to thirty inches of rise, with a level landing before the next run. That gives a sensible ceiling for a home ramp too.
The Bottom Line
Choosing wheelchair ramp length is a measurement, a ratio, and a rounding decision. Measure the total rise including any lip, apply the slope the manufacturer specifies for that model with the ADA figure of 1:12 as your default reference, and round up to the next available length. Then walk the run and confirm both ends land on level ground with somewhere flat at the top to stop and open a door. If the number that comes out is longer than you can fit, store, or lift, that is the signal to move past the portable category. Run the arithmetic in our ramp length calculator.