Australia uses 1:14. America uses 1:12. That difference is metres.
Search "ramp calculator" and most of what comes back is American. The US accessibility rule caps a ramp at 1:12 — one unit of rise for every twelve of run. In Australia, the general access ramp gradient under AS 1428.1 is 1:14. We are stricter.
Build an Australian ramp off a 1:12 answer and it comes out too steep, and it comes out short. Take a 900mm rise, which is roughly a typical Queenslander landing or three or four steps:
- Australia, 1:14: 900 × 14 = 12,600mm of sloped run
- United States, 1:12: 900 × 12 = 10,800mm
- Difference: 1,800mm — nearly two metres of yard you did not budget for
Two metres decides whether a ramp fits down the side of a house, whether it clears a driveway, and whether the quote you gave is the job you can build. Better to find out now than with the bearers down.
Run needed for a given rise
| Rise | Run at 1:14 (Australia) | Run at 1:12 (US) | Extra you need here |
|---|---|---|---|
| 150mm | 2,100mm | 1,800mm | 300mm |
| 300mm | 4,200mm | 3,600mm | 600mm |
| 450mm | 6,300mm | 5,400mm | 900mm |
| 600mm | 8,400mm | 7,200mm | 1,200mm |
| 900mm | 12,600mm | 10,800mm | 1,800mm |
| 1,200mm | 16,800mm | 14,400mm | 2,400mm |
Sloped run only. Landings are on top of every one of those figures.
Landings: the bit that blows the footprint out
A ramp is not allowed to run forever without a flat rest. Under AS 1428.1 a single flight of a 1:14 ramp runs up to 9 metres before it needs a landing. At 1:14, nine metres of run only buys you 9,000 ÷ 14 = 643mm of rise per flight.
So the 900mm rise above cannot be done in one go. Work it through:
- 900mm of rise ÷ 643mm per flight = 1.4, rounded up to 2 flights
- Two flights means 1 intermediate landing between them, at 1,200mm
- Total ramp: 12,600 + 1,200 = 13,800mm
- Plus a landing at the top and one at the bottom — another 1,200mm each, so about 16.2 metres of ground from end to end
The American answer for the same job was 10.8 metres. The real one is over sixteen. That is the whole reason this page exists.
Two more things about landings. A straight-through landing is 1,200mm long, but a landing where the ramp turns — a switchback, which is how most ramps fit into a suburban yard — has to be bigger, because a wheelchair turns on it. Around 1,540mm is the figure Australian access guidance publishes. And the top landing has to be big enough to open the door from, which people forget until the door swings into the slope.
The other gradients, and when each one applies
| Type | Gradient | As a percentage | Where it fits |
|---|---|---|---|
| Walkway | 1:20 | 5.0% | Gentle grade. No landing needed until 15m of run. |
| Ramp | 1:14 | 7.1% | The general access ramp. Landing every 9m of run. |
| Step ramp | 1:10 | 10.0% | Small rises only — up to about 190mm, one step's worth. |
| Kerb ramp | 1:8 | 12.5% | Kerbs. Short, steep, up to about 190mm of rise. |
Step ramps and kerb ramps are not shortcuts around the 1:14 rule. They exist for very small height changes and they stop existing the moment the rise goes past roughly 190mm. If you have 400mm to climb, you are building a ramp, not a long step ramp.
If you have the room, 1:20 is worth considering even where 1:14 is allowed. It is noticeably easier to push a chair up, it is easier to control coming down, and it does not need a landing until 15 metres of run. The trade-off is length — 900mm of rise at 1:20 is 18 metres of run before landings.
What the calculator does not cover
Gradient and landings are the geometry. A real access ramp has more to it than that, and all of it sits outside a calculator:
- Handrails on ramps, at set heights, continuous, and extending past the ends.
- Edge protection along the sides so a wheel cannot run off.
- Width — a clear width between the rails, not the width of your framing.
- Surface — slip resistance, which matters more on a wet ramp than on a wet path.
- Crossfall — a ramp cannot tip sideways much, so bearers have to be level across as well as graded along.
- Tactile indicators in some situations.
NDIS home modifications
This is where most domestic builders and carpenters meet ramps. An NDIS home modification — a ramp so someone can get in and out of their own house — is normally specified by an occupational therapist and built to AS 1428.1. The OT's report will nominate the gradient and the layout, and it is worth reading before you price, because a switchback with two landings is a very different job from a straight run down the side.
Quote the landings. They are flat framed platforms with their own bearers and their own footings, and a ramp quoted as "12.6 metres of decking" loses money the moment two landings turn up in it.
When to bring in an access consultant
Anything for public access — a shop, a clinic, a community hall, a workplace, common property in a unit block — needs an access consultant, and usually a building surveyor as well. The rules there go well beyond gradient and getting it wrong is expensive to unbuild. Say it plainly at quote time: on a public-access job the ramp design comes from a consultant, and you build to it.
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What is the maximum ramp gradient in Australia?
AS 1428.1 sets the general access ramp gradient at 1:14 — one of rise for every fourteen of run, about 7.1%. That is stricter than the American 1:12 rule you will find on most overseas calculators.
Why is the Australian ramp rule different from the ADA 1:12?
They are different countries with different rules. The ADA is American law and does not apply here. Australia uses AS 1428.1, and its general ramp gradient of 1:14 is gentler than 1:12 — so an Australian ramp needs more run for the same rise.
How long does a ramp need to be for a 900mm rise?
At 1:14, 900 × 14 = 12,600mm of sloped run. But a flight can only run 9m before it needs a landing, which caps one flight at about 643mm of rise, so 900mm takes two flights and a 1,200mm landing between them — 13,800mm of ramp, plus landings at each end.
How often does an Australian ramp need a landing?
A 1:14 ramp runs up to 9 metres between landings, which is about 643mm of rise per flight. A 1:20 walkway can run 15 metres. You also need a level landing at the top and at the bottom.
How big does a ramp landing need to be?
A straight-through landing is 1,200mm long. A landing where the ramp turns back on itself needs more — around 1,540mm — because a wheelchair has to turn on it. Allow the bigger figure any time you are planning a switchback.
When can I use a 1:8 or 1:10 ramp?
Only for very small height changes — kerb ramps and step ramps top out at around 190mm of rise. They are not a way to shorten a bigger ramp. Past that rise you are building a 1:14 ramp with landings.
Do I need an access consultant?
For anything public-facing or needing sign-off, yes — a shop, workplace, clinic or common property in a unit block. An access consultant sets the design and you build to it. For a private home modification, the specification usually comes from an occupational therapist.
Other calculators you'll want
General information for Australian trades, and an estimate only — not tax, financial or legal advice. It is not engineering, building or design advice either: a calculator works out a quantity from the figures you enter, and anything that needs sign-off still needs your engineer, certifier or building surveyor. Australian Standards are published and sold by Standards Australia, so no clause text is reproduced here. The gradients, maximum runs between landings and landing lengths above are described in our own words from published Australian access guidance on AS 1428.1, and editions change. This is a layout and materials estimate, not an access design. For anything requiring sign-off — public access, a workplace, or a building approval — the design should come from an access consultant or your building surveyor.