Stair calculator
Choose the kind of stair, then enter the riser, the going and the number of risers. The section redraws as you type, 2R + G is tested against the right row for a house, a public stair, a private stair, a spiral or an attic stair, and every check names its clause.
What it checks
The same engine as the calculator in AEC Assistant, with every table checked against NCC 2025 or the Standard it calls up. The same inputs always give the same result.
Background: NCC stair requirements guide
You enter
- Kind of stair: public, private (within a sole-occupancy unit), house, spiral or attic
- Riser and going in millimetres
- Number of risers in the flight
- Whether it is an accessible stair, for the AS 1428.1 checks
It reads from
- NCC 2025 Volume One Table D3D14 and D3D15
- NCC 2025 Housing Provisions Tables 11.2.2a and 11.2.2b, clause 11.2.4
- AS 1428.1:2021 Section 8
A worked example
The calculator's example inputs, checked.
Slope relationship
630 mm
2R + G · riser 175 / going 280
Complies with NCC 2025 Vol 1 Table D3D14 (Public) on the figures entered. The requirements marked for checking still apply on site.
- Slope relationship2R + G = 2 × 175 + 280 = 630 mmNCC 2025 Vol 1 Table D3D14 (Public)
- Riser175 mm · limit 115–190 mmNCC 2025 Vol 1 Table D3D14 (Public)
- Going280 mm · limit 250–355 mmNCC 2025 Vol 1 Table D3D14 (Public)
- Risers per flight10 · limit 2–18NCC 2025 Vol 1 D3D14(1)(a)
Questions
What riser and going does the NCC allow?
A riser of 115 to 190 mm and 2R + G between 550 and 700 mm for every stair; the going is 240 to 355 mm for a house or a private stair and 250 to 355 mm for a public stair. A spiral stair in a house has its own row. The calculator applies the table for the stair type you choose.
Which NCC edition does the calculator use?
NCC 2025: Volume One Table D3D14 and Housing Provisions Tables 11.2.2a and 11.2.2b, with AS 1428.1:2021 for an accessible stair.
Does it check an accessible stair?
Yes. Answer yes to the accessible stair question and the AS 1428.1:2021 requirements for opaque risers, the nosing profile, the contrasting nosing strip and handrails on both sides are listed beside the result. The riser, going and 2R + G are still checked against the table row for the stair type you chose.
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Ask about the stairs on your own project
The free plan answers from the National Construction Code, state building and planning legislation, ABCB handbooks, regulator practice notes and codes of practice, with the clause cited. Plus adds the Standards, including AS 1428.1:2021, from A$79 a month plus GST.