Outdoor
ADA ramp slope calculator
One foot of ramp for every inch of rise at 1:12 — that part is a multiplication. What decides whether you can build it is the footprint, and the landings are added to the ramp rather than included in it. This works out the whole rectangle, folds it into a switchback if it will not fit, and keeps the ADA rules apart from the residential ones, because they are not the same and the difference is usually in your favour.
Written and edited by Pablo Ruiz Quintero
Last reviewed 2026-09-21 · Nothing you type leaves your browser
The height, and the space you have
The ramp length is a multiplication and you do not need a website for it. What you need is the footprint, because the landings are as long as a run and a ramp that turns is twice as wide. That is the part that decides whether it fits.
Ground to the top landing surface — which is the threshold, not the door sill. Measure on the ground as it will be, not as it slopes now.
From the step out to the fence, the path or the drive. Leave it if you do not know — the straight footprint is shown either way.
The ADA does not apply to a private residence. The IRC does, and it is more forgiving: 36 inch landings, no 30 inch rule on rise between them, handrails on one side, and an explicit exception down to 1:8 where the site will not take 1:12.
The steepest a public ramp may be. It is a limit, not a target: a person self-propelling up it is lifting a twelfth of their own weight the whole way, and many cannot.
The demanding case, and the one the maximum was never meant for. Pushing up a 1:12 means lifting a twelfth of your weight continuously, and the same slope going down needs braking the whole way.
The ADA minimum, measured between the handrails and not between the edges of the deck.
The cheapest to build and the most common. It needs footings below the frost line, it needs a slip-resistant surface — bare wet decking is a hazard, not a ramp — and when it is no longer needed it is worth nothing and costs money to remove.
Used only to pick a regional labour rate. It stays in your browser.
2 legs, folded
30 ft
of ramp · footprint 21 × 6 ft · 36 ft to travel
It will not go straight — it has to turn
36 ft straight will not go in 30, so it folds into 2 legs and the footprint becomes 21 by 6 ft. Every turn needs a flat landing big enough to stop, turn and start again.
Worth knowing before you give up on it
The ADA does not apply to your house
It is a civil rights law about places open to the public. A ramp at a private home is governed by the residential code, which allows 36 in landings instead of 60, sets no limit on rise between them, wants a handrail on one side rather than two, and contains an explicit exception down to 1:8 where the site will not take 1:12.
At 1:8 this ramp is 20 ft instead of 30 ft. Steep, and sometimes the difference between a ramp and no ramp at all.
Every slope, on your rise
The ramp surface only — landings are added on top of all of these.
| Slope | Grade | Ramp | ADA |
|---|---|---|---|
| 1:20 | 5% | 50 ft | yes |
| 1:16 | 6.25% | 40 ft | yes |
| 1:12 · yours | 8.33% | 30 ft | yes |
| 1:10 | 10% | 25 ft | no |
| 1:8 | 12.5% | 20 ft | no |
Below 1:20 the ADA stops calling it a ramp and calls it a walking surface — and the handrail and landing requirements go with the name. Where the ground allows it, that is the cheapest compliance there is.
The footprint, to scale
Plan view. The slope does not show here — this is about whether it fits.
What gets built
- Deck, 117 ft²
30 ft of ramp plus 3 landings, 36 in wide. Add 9 in to that if you fit handrails later — the clear width is measured between them.117 ft² - Footings
Below the frost line, one pair every six feet. The reason a timber ramp needs a permit and a modular aluminium one usually does not.10
What it costs
National average. Pressure-treated timber, built on site, deck, landings and footings. Not included: the permit, moving a gas meter or a downspout out of the way, and any regrading where the bottom landing lands.
Fifteen to twenty years treated, less if it never gets sealed and the deck stays wet. Worth pricing against modular aluminium before committing: it goes up in a day, needs no footings, and can be rented by the month if the need is temporary. If the ramp is replacing steps rather than joining them, see the stair calculator.
Worth knowing
- 30 in of rise at 1:12 is 30 ft of ramp surface. That number is the easy part — what decides whether you can build it is the footprint, which is 36 ft in a straight line once the landings are counted.
- This is a private home, so the ADA does not apply to it — it is a civil rights law about places open to the public. The IRC is what governs, and it is more forgiving: 36 in landings instead of 60, no limit on rise between them, handrails on one side, and an explicit exception permitting 1:8 where the site makes 1:12 technically infeasible. A great many people are told they cannot build a ramp that their code would in fact allow.
- For a self-propelled manual chair, 1:12 is legal and hard. The demanding case, and the one the maximum was never meant for. Pushing up a 1:12 means lifting a twelfth of your weight continuously, and the same slope going down needs braking the whole way. At 1:16 the ramp becomes 40 ft instead of 30 — longer, and the difference between a ramp that gets used and one that gets avoided.
- It does not fit straight in 30 ft, so it folds into 2 legs with 1 turning landing. The footprint becomes 21 by 6 ft. A 180° turn needs a landing at least 36 in square — the chair has to stop, turn and start again on the flat, and a turn taken on the slope is the commonest way a home-built ramp becomes unusable.
- At this slope and rise the residential code does not require a handrail — R311.8.3 only asks for one where the slope exceeds 1:12, and a guard only above 30 in of drop. Fit one anyway. The code is a floor, and this is one of the places it sits below common sense: somebody using a walker or steadying themselves holds the rail, not the ramp, and a person who falls on a ramp with nothing to grab falls all the way to the bottom.
On this page — 6 sections
The length is the easy part. The footprint is the question
The short version
- One foot of ramp per inch of rise at 1:12. That much is a multiplication, and it is not what people actually need to know.
- Landings are added, not included. A 30 in rise is 30 ft of ramp and about 40 ft of footprint once they are counted.
- The ADA does not apply to a private home, and the residential rules are meaningfully more forgiving.
- 1:12 is a maximum, not a target. The same standard recommends 1:16 to 1:20 where there is space.
Every ramp calculator on the internet does the same thing: you give it a height, it multiplies by twelve, it gives you a length. That is genuinely all most of them do, and it answers a question nobody is really asking.
What people are asking is will this fit. And the ramp length is not the footprint, because a ramp is not only ramp.
Take thirty inches of rise — a typical porch, three or four steps.
| 30 in of rise at 1:12 | At a business | At a home |
|---|---|---|
| Ramp surface | 30 ft | 30 ft |
| Bottom landing | 5 ft | 3 ft |
| Top landing | 5 ft | 3 ft |
| Straight footprint | 40 ft | 36 ft |
| And at 36 in of rise | 51 ft | 42 ft |
That last row is the one worth sitting with. Six more inches of rise adds eleven feet to an ADA footprint, not six — because crossing thirty inches of rise triggers an intermediate landing, and a landing is five feet of ground that gains no height at all.
Forty feet does not fit in most front gardens. Fifty-one certainly does not. So the ramp folds, and folding is where the second thing nobody calculates arrives: a 180 degree turn needs a landing big enough to stop on, turn on and start again on — sixty inches square — and every extra leg doubles the width of the footprint.
US Department of Justice, 2010 ADA Standards for Accessible Design — Chapter 4, Accessible Routes (2010) · checked 2026-09-21
The ADA does not apply to your house
This is the most useful thing on the page and it is almost never said plainly, so here it is plainly.
The Americans with Disabilities Act is a civil rights law. It covers places of public accommodation and commercial facilities — shops, restaurants, offices, clinics, anywhere the public is invited. It does not govern what you build at your own home for your own family.
What governs a ramp at a private house is the residential building code, and it is a different and gentler set of numbers. People arrive at the 1:12 rule, do the arithmetic, find they need forty feet they have not got, and conclude a ramp is impossible. Quite often it is not.
| ADA — public and commercial | IRC — a private home | |
|---|---|---|
| Maximum slope | 1:12 | 1:12, with an exception to 1:8 |
| Landings top and bottom | 60 in | 36 in |
| Landing every 30 in of rise | Required | Not required |
| Handrails | Both sides, above 6 in of rise | One side, above 1:12 |
| Clear width | 36 in between handrails | 36 in |
| Turning landing | 60 × 60 in | 36 in, and never less than the width |
| Enforced by | Complaint and lawsuit | Building inspection |
International Code Council, International Residential Code — R311.8, Ramps (2021) · checked 2026-09-21
1:12 is the steepest allowed, which is not the same as suitable
The number 1:12 has taken on a life of its own. It is treated as the accessible slope, the target, the thing to hit. It is none of those. It is a ceiling, set where it is because a strong person with good technique can manage it — and the ADA’s own advisory text recommends 1:16 to 1:20 wherever there is room.
The physics is not subtle. On a 1:12 slope, a person pushing themselves is working against one twelfth of the combined weight of themselves and the chair, continuously, for the whole length of the ramp. For a 180 pound person in a 30 pound chair that is about seventeen pounds of force through the pushrims, up thirty feet, in whatever weather there is. Coming down it is the same seventeen pounds of braking through the palms of the hands.
8.33%
1:12, the ADA maximum
4.76° — a limit, not a target
6.25%
1:16, what the ADA recommends
A third longer, and a different experience
1:20
Below this it is not a ramp
It becomes a walking surface, with no handrail rule
1:48
Maximum cross slope
A chair on a side slope steers itself downhill
That last figure is the one people have never heard of and it matters as much as the running slope. Cross slope is the tilt across the width of the ramp, and the ADA caps it at 1:48 — barely perceptible. On any more than that a chair wanders downhill and the user has to correct continuously with one arm while pushing with both, which is exactly as difficult as it sounds. Timber ramps acquire cross slope when a footing settles, and it is invisible until somebody tries to use it.
And the other end of the scale is worth knowing about because it is free money: below 1:20 the ADA stops calling it a ramp. At that gradient it is a walking surface, and the handrail requirement, the landing requirement and the edge protection requirement all go with the name. Where a site has the room to run long and shallow — a garden path graded up to the door rather than a structure bolted to it — that is the cheapest compliance there is, and it looks like landscaping rather than equipment.
Landings, turns, and the door at the top
Landings do the work that makes a ramp usable, and they are the first thing shortened when the footprint will not fit. Each one exists for a reason worth knowing before trimming it.
- 01The bottom landingA flat place to arrive at and set off from. Without it the chair meets the slope at whatever angle the path happens to be, and a footplate can catch as the geometry changes.
- 02Intermediate landingsUnder the ADA, one for every 30 inches of rise. They are rest points — somewhere to stop halfway up without rolling backwards — and they are the reason a tall ramp is far longer than the multiplication suggests.
- 03Turning landings60 by 60 inches, and never narrower than the ramp. A chair must stop, turn through 180 degrees and start again, all of it on the flat. A turn taken on the slope is the classic home-built failure.
- 04The top landingWhere the ramp meets the door, and the one most often got wrong. It has to be deep enough that somebody in a chair can reach the handle, pull the door open past themselves, and get through.
The details that get left out
- Handrail extensions — 12 in horizontally past the top and bottom of every run. It is what somebody holds while they get their feet settled, and it is the first thing trimmed to make a ramp fit.
- Edge protection along the open sides, so a wheel cannot run off. A curb, a barrier, or the deck surface extended beyond the handrail.
- Clear width measured between the handrails, not across the deck — so 36 in clear means building about 45 in wide.
- A slip-resistant surface. Bare wet decking is not a ramp, it is a slide, and a broom finish on concrete should run across the slope rather than along it.
- Handrails at 34 to 38 in above the ramp surface, graspable — a 2 × 4 laid flat is not, whatever it looks like.
- Drainage at the bottom landing, because it is now the lowest point of a large sloping surface and water goes there.
- Lighting, because the ramp will be used after dark and a step-free route is only step-free if you can see it.
- Where the ramp lands: a path, not grass. Wheels on wet lawn defeat the entire exercise in the last four feet.
Timber, aluminium or concrete — and how long you need it
Almost everybody starts by asking which material is best, and it is the wrong first question. The right one is how long the ramp is needed for, because the answer to that changes the material entirely.
After a hip replacement, three months. For a parent moving in, years. In hospice, weeks. A timber ramp is a permanent answer to all three, and for two of them it is the wrong one — it takes a week to build, needs a permit and footings below the frost line, and when it is no longer needed it is worth nothing and costs money to take away.
| Built from | Per ft² installed | Footings | What it really is |
|---|---|---|---|
| Pressure-treated timber, built on site | $45 | Yes | The cheapest to build and the most common. It needs footings below the frost line, it needs a slip-resistant surface — bare wet decking is a hazard, not a ramp — and when it is no longer needed it is worth nothing and costs money to remove. |
| Modular aluminium, bolted together | $54 | No | Handrails and a slip-resistant surface are part of the sections, so the price is all in. It goes up in a day on gravel pads rather than footings, it usually needs no permit because it is not a permanent structure, it comes down in a day, and it resells for a serious fraction of what it cost. It can also simply be rented. |
| Poured concrete | $44 | No | Cheapest per square foot of surface and dearest overall, because a ramp is not flatwork: it needs fill, forming on a slope, reinforcement and a broom finish across the run rather than along it. It is also the only one that cannot be undone. |
Concrete deserves a word because the per-square-foot figure above misleads. It is the cheapest surface in the table and the most expensive ramp, because a ramp is not flatwork: it needs fill compacted in lifts, forming on a slope, reinforcement, and a broom finish run across the direction of travel rather than along it. It is also the only one of the three that cannot be undone, and the only one that looks like part of the house rather than equipment attached to it.
MaterialsEstimator, Access ramp price survey — timber, modular aluminium and concrete · checked 2026-09-21
What goes wrong
01Calculating the ramp length and calling it the footprint
Landings gain no height and they are added to the ramp, not included in it. A 36 inch rise at 1:12 is 36 feet of ramp and 51 feet of ADA footprint, because crossing 30 inches of rise triggers an intermediate landing.
Instead — Work out the footprint before anything else, and measure the space you actually have. It is the number that decides whether the project is straight, folded, or not a ramp at all.
02Assuming the ADA applies to a private home
It is a civil rights law about places open to the public. Applying its 60 inch landings and its 30 inch rise rule to a house makes a ramp look impossible on plenty of lots where the residential code would allow one.
Instead — Use the residential rules for a residence: 36 inch landings, no rise limit between them, and an explicit exception down to 1:8 where the site will not take 1:12.
03Building to 1:12 because it is the rule
It is the maximum, not the recommendation. Somebody self-propelling up a 1:12 is lifting a twelfth of their weight the whole way, and the ADA's own advisory text asks for 1:16 to 1:20 where there is space.
Instead — Pick the slope for the person who will use it. If there is room to go shallower, go shallower — it is the difference between a ramp that gets used and one that gets avoided.
04Framing the deck at 36 inches wide
The ADA's 36 inches is clear width between the handrails. Fit the rails to a 36 inch frame and the clear width is about 27 — it fails an inspection it was designed to pass, and a wide chair catches the rails at every turn.
Instead — Build about 45 inches wide for 36 clear, and check the number your own rail system takes rather than assuming.
05Taking the turn on the slope
A switchback without a flat landing at the fold asks somebody to turn 180 degrees while holding themselves against a gradient. It is the commonest reason a home-built ramp turns out to be unusable by the person it was built for.
Instead — A flat landing at every fold, 60 by 60 inches and never narrower than the ramp. If there is not room for it, the ramp does not fold there.
06Forgetting the door at the top
An outward-opening door has to be pulled past the person in the chair. That needs landing depth and 18 inches of clear space beyond the latch side — and nothing about the ramp itself will tell you it is missing.
Instead — Check the manoeuvring clearance before you set the top landing size, or rehang the door to swing inward, which is often the cheaper fix by a long way.
07Cutting the handrail extensions off to make it fit
The 12 inches of horizontal rail beyond each end is what somebody holds while they get their feet settled at the transition. Losing it costs the support exactly where the surface changes.
Instead — Count the extensions into the footprint from the start. If the ramp only fits without them, the ramp does not fit.
08Building permanently for a temporary need
A timber ramp takes a week, needs a permit and footings, and is worth nothing afterwards. A great many are built for a three-month recovery and are still in the garden years later.
Instead — Ask how long it is needed for. Modular aluminium rents for around $264 a month at thirty feet, goes up in a day, comes down in a day and resells if bought.
- 01Measure the rise properlyFrom the ground where the ramp will land, up to the finished surface of the top landing — not to the door sill, and not to the top step. Hold a level out from the doorway and measure straight down at the far end.
- 02Decide which rules applyA business or anywhere open to the public is ADA. A private home is the residential code, which is a different and more forgiving set of numbers.
- 03Pick the slope for the person, not the limit1:12 is the steepest the ADA allows, not a target. Somebody pushing their own chair wants 1:16 or shallower, and the ADA itself says so.
- 04Multiply for the ramp lengthRise in inches times the ratio gives the ramp surface in inches. Thirty inches of rise at 1:12 is thirty feet of ramp.
- 05Add the landingsOne at the top, one at the bottom, one at every turn, and under the ADA one for every 30 inches of rise. They add to the length and gain no height at all.
- 06Measure the space you actually haveOut to the fence, the path, the drive. If the straight footprint will not fit, the ramp has to fold — and each fold needs a landing big enough to turn a chair on the flat.
- 07Check what happens at the doorThe top landing has to let somebody in a chair reach the handle and pull the door open past themselves. A ramp that arrives at a door with no room to open it is not finished.
Most ramps are built alongside an existing flight rather than replacing it, and the two have to agree about where the landing is. That page works out rise, run and headroom from the same total height.
If the ramp is going beside the steps- Running slope
- The slope along the direction of travel, written as a ratio of run to rise. 1:12 means twelve inches forward for every inch up, which is 8.33 per cent and 4.76 degrees.
- Cross slope
- The slope across the width of the ramp. The ADA limits it to 1:48, because a chair on a sideways slope steers itself downhill and the user has to fight it the whole way.
- Rise
- The vertical height being climbed, measured to the finished surface of the top landing rather than to the door sill. Getting this wrong by the thickness of a threshold is how a ramp ends up an inch short.
- Landing
- A level platform at the top, at the bottom, at every change of direction, and — under the ADA — every 30 inches of rise. It gains no height, and it is added to the ramp length rather than included in it.
- Switchback
- A ramp folded back on itself through 180 degrees to fit a shorter space. It needs a turning landing at each fold, and it roughly doubles the width of the footprint for each extra leg.
- Clear width
- The 36 inches the ADA requires, measured between the handrails rather than across the deck. Handrails eat about 4.5 inches a side, so the deck has to be built wider than the number in the standard.
- Handrail extension
- The 12 inches a handrail must continue horizontally past the top and bottom of each run. It is what somebody holds while they get their feet settled, and it is the first thing cut off when a ramp will not fit.
- Edge protection
- A curb, barrier or extended surface along the open sides of a ramp, so a wheel cannot run off the edge. Required by the ADA and routinely missing from home-built ramps.
- Manoeuvring clearance
- The space a door needs on the landing so somebody in a chair can get at the handle and pull it open — 60 inches deep and 18 inches past the latch side for a front approach. A ramp arriving at a door with no room to open it is a finished ramp nobody can use.
- Technically infeasible
- The phrase the residential code uses to allow a steeper ramp. It means the site genuinely will not take a compliant slope, not that a compliant one would be inconvenient, and it is the basis of the 1:8 exception.
- Threshold
- The strip under the door. Anything over half an inch is a barrier in its own right, and a ramp that delivers a chair perfectly to a three-quarter inch threshold has not finished the job.
- Platform lift
- A powered vertical lift, the answer when the rise is too great or the site too small for any ramp. More expensive, needs power and servicing, and occasionally the only honest option.
Common questions
- How long does a wheelchair ramp need to be?
- One foot of ramp for every inch of rise at the ADA maximum of 1:12. A 30 inch rise is 30 feet of ramp — but that is the ramp surface, not the footprint. Add a landing at the top and the bottom, and under the ADA another for every 30 inches of rise, and the same ramp occupies about 40 feet in a straight line. The footprint is the number that decides whether you can build it.
- What is the maximum slope for a wheelchair ramp?
- 1:12 under the ADA — 8.33 per cent, or 4.76 degrees. It is a maximum and not a recommendation: the same standard suggests 1:16 to 1:20 where space allows, because somebody pushing their own chair up a 1:12 is lifting a twelfth of their body weight continuously and many people cannot do it at all.
- Does the ADA apply to a ramp at my house?
- No. The ADA is a civil rights law covering places of public accommodation and commercial facilities — shops, offices, restaurants, clinics. A ramp you build at your own home is governed by the residential code, which is more forgiving: 36 inch landings instead of 60, no limit on rise between them, a handrail on one side rather than two, and an explicit exception permitting 1:8 where site constraints make 1:12 technically infeasible. A lot of people are told they cannot build a ramp that their own code would allow.
- Can a residential ramp be steeper than 1:12?
- Yes. The IRC sets 1:12 as the standard and then allows 1:8 — 12.5 per cent — where it is technically infeasible to do better because of site constraints. That is a real allowance and not a loophole, and on a tight urban lot it is frequently the difference between a ramp and no ramp. It is steep: hard to self-propel up and needing real braking coming down, so it suits an attended chair or a power chair far better than a manual one.
- How many landings does a ramp need?
- One at the top, one at the bottom, and one at every change of direction — those apply everywhere. The ADA adds one more rule that the residential code does not have: a landing for every 30 inches of rise. So an ADA ramp climbing 36 inches needs an intermediate landing part way up, which adds five feet to the footprint and gains nothing in height.
- How big does a turning landing have to be?
- 60 by 60 inches under the ADA, and never narrower than the ramp itself. A chair has to come to a stop, turn through 180 degrees and start again, all on the flat — a turn taken on the slope is the single most common reason a home-built switchback turns out to be unusable by the person it was built for.
- How wide should a wheelchair ramp be?
- 36 inches clear is the ADA minimum, and the word doing the work is "clear": it is measured between the handrails, not across the deck. Handrails take roughly 4.5 inches a side, so a compliant 36 inch ramp is built about 45 inches wide. A ramp framed at exactly 36 and then fitted with rails fails an inspection it was designed to pass.
- What does a wheelchair ramp cost?
- A timber ramp runs roughly $45 a square foot of deck installed, plus handrails and footings — so a 30 foot ramp with its landings is usually a few thousand dollars. Modular aluminium is more per square foot at around $54, and the handrails and the slip-resistant surface are already in that. Concrete is the cheapest surface and the dearest ramp, because a ramp is not flatwork.
- Should I build a ramp or rent one?
- Ask how long it is needed for first, because it changes the answer completely. After a hip replacement it is three months; for a parent moving in it is years; in hospice it may be weeks. Modular aluminium rents for around $264 a month for a 30 foot ramp, and it scales with the size rather than being a flat fee. It goes up in a day on gravel pads rather than footings, comes down in a day, and resells. A timber ramp is a permanent answer to a question that is often temporary, and it is still in the garden four years later.
- Do I need a permit for a wheelchair ramp?
- Usually yes for a timber or concrete ramp, because it is a permanent structure on footings and it is attached to the house. Modular aluminium frequently does not need one, precisely because it is freestanding, bolted rather than built, and removable — that is one of the quieter reasons it gets chosen. Ask the building department; the answer is local and the call is short.
- What slope is best for someone pushing their own chair?
- 1:16 or shallower. The ADA maximum was set as an upper limit for what is achievable, not as a comfortable gradient, and the difference is physical: at 1:12 you are lifting a twelfth of your weight the whole way up and braking against the same fraction coming down, in the rain, on a surface that may be wet. At 1:16 the ramp is a third longer and it is the difference between one that gets used and one that gets avoided.
- What if there is not enough room for a ramp at all?
- Then say so early rather than building something steep and unusable. The options in order are: start the ramp further out into the site, which is often possible and rarely considered; fold it into a switchback, which costs width instead of length; move the entrance to a different door with less rise; or fit a platform lift, which needs power and servicing and is the honest answer when the rise is large and the site is small.
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About the author
Pablo Ruiz Quintero — Editor
Editor of MaterialsEstimator. Decides which documents count as a source, what every default value is, and where the line sits between what the reader parses and what the engines compute.
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