Stair Calculator Australia - Rise, Going and 2R + G
Calculate risers, goings, total run, stringer length and pitch for any Australian staircase. Every result is checked live against NCC 2022 - riser 115-190 mm, going 240-355 mm (private) or 250-355 mm (public), 2R + G 550-700 mm, and 2-18 risers per flight.
Advanced options
Compliant Stair Setout
Full Stair Breakdown
| Parameter | Value | NCC 2022 check |
|---|
Use This Stair Calculator for Australian Homes and Commercial Buildings
Enter your total floor-to-floor rise and either the total run or your desired going. The calculator returns the exact riser height, going, 2R + G value, stringer length, pitch and NCC compliance status.
Worked Example - 2.7 m Floor-to-Floor Stair
This is the most common residential stair in Australia. A 2.7 m floor-to-floor rise with a comfortable going.
| Parameter | Value | NCC 2022 limit | Status |
|---|---|---|---|
| Total rise | 2,700 mm | — | — |
| Number of risers | 16 | 2-18 per flight | Pass |
| Riser height (R) | 168.75 mm | 115-190 mm (private) | Pass |
| Going (G) | 280 mm | 240-355 mm (private) | Pass |
| 2R + G | 617.5 mm | 550-700 mm | Pass |
| Total run | 4,200 mm | — | — |
| Stringer length | 5,017 mm | — | — |
| Pitch | 32.7° | 30-38° typical | Pass |
NCC 2022 Stair Dimensions - Residential vs Commercial
These are the Deemed-to-Satisfy limits under NCC 2022 Volume Two (Housing Provisions 11.2.2) and Volume One (D3D14). Always confirm with your certifier for the specific building classification.
| Dimension | Residential / private | Commercial / public |
|---|---|---|
| Riser (R) | 115 - 190 mm | 115 - 190 mm |
| Going (G) | 240 - 355 mm | 250 - 355 mm |
| 2R + G | 550 - 700 mm | 550 - 700 mm |
| Risers per flight | 2 - 18 | 2 - 18 (36 in Class 9b with direction change) |
| Minimum stair width | 600 mm | 1,000 mm |
| Headroom | 2,000 mm min | 2,000 mm min |
| Landing depth | ≥ stair width | ≥ stair width |
| Open riser gap | 125 mm sphere must not pass | 125 mm sphere must not pass |
Common Stair Configurations for Australian Homes
Typical floor heights and the compliant setout that fits them. All assume 2R + G in the comfortable 600-640 mm range.
| Floor height | Risers | Riser height | Going | 2R + G | Total run |
|---|---|---|---|---|---|
| 2,400 mm | 14 | 171 mm | 278 mm | 620 mm | 3,614 mm |
| 2,550 mm | 15 | 170 mm | 280 mm | 620 mm | 3,920 mm |
| 2,700 mm | 16 | 169 mm | 280 mm | 618 mm | 4,200 mm |
| 2,850 mm | 16 | 178 mm | 270 mm | 626 mm | 4,050 mm |
| 3,000 mm | 17 | 176 mm | 275 mm | 627 mm | 4,400 mm |
| 3,150 mm | 18 | 175 mm | 275 mm | 625 mm | 4,675 mm |
How the Stair Calculator Works
Every result uses the standard Australian stair setout method and checks each dimension against the NCC 2022 Deemed-to-Satisfy limits.
- Number of risers = total rise ÷ ideal riser height, rounded to the nearest whole number (then adjusted to keep the riser within 115-190 mm).
- Riser height = total rise ÷ number of risers. Every riser must be equal within 5 mm.
- Treads = risers − 1 for a standard stair (the top floor level acts as the final landing, not a tread).
- Going = either your target going, or total run ÷ number of treads.
- 2R + G check = (2 × riser) + going. Must be between 550 mm and 700 mm.
- Total run = number of treads × going.
- Stringer length = √(total rise² + total run²).
- Pitch = tan⁻¹(total rise ÷ total run).
- Compliance is checked live for riser, going, 2R + G and flight length.
Stair Formulas Used
- Number of risers = round(total rise ÷ ideal rise)
- Riser height (R) = total rise ÷ number of risers
- Number of treads = number of risers − 1
- Going (G) = target going, or total run ÷ number of treads
- 2R + G = 2 × riser + going
- Total run = treads × going
- Stringer length = √(rise² + run²)
- Pitch angle = arctan(rise ÷ run)
Worked example: Total rise 2,700 mm. Ideal rise 175 mm. 2700 ÷ 175 = 15.43, round to 16 risers. Riser = 2700 ÷ 16 = 168.75 mm (within 115-190 mm). Treads = 15. Target going = 280 mm. 2R + G = 2(168.75) + 280 = 617.5 mm (within 550-700 mm). Total run = 15 × 280 = 4,200 mm. Stringer = √(2700² + 4200²) = 5,017 mm. Pitch = arctan(2700 ÷ 4200) = 32.7°. All NCC checks pass.
Frequently Asked Questions - Stairs in Australia
What is the 2R + G rule and why does it matter?
2R + G is the comfort formula: twice the riser height plus the going must fall between 550 mm and 700 mm under NCC 2022. The ideal target is about 620 mm. A 175 mm riser with a 275 mm going gives 625 mm - right in the comfortable range. If your 2R + G is below 550 mm the stair is too steep and cramped; above 700 mm it feels unnatural to climb. The calculator checks this automatically.
What is the maximum riser height in Australia?
Under NCC 2022, the maximum riser height is 190 mm for both residential and commercial stairs. The minimum is 115 mm. For commercial stairs some guidance recommends a maximum of 180 mm, but the Deemed-to-Satisfy limit is 190 mm. Always confirm with your certifier for your specific building classification.
What is the minimum going (tread depth) in Australia?
The minimum going is 240 mm for private stairways (houses) and 250 mm for public stairways (commercial and public buildings). The maximum going is 355 mm for both. A going below 240 mm makes the stair unsafe to descend; above 355 mm people tend to skip steps and trip.
How many risers can I have in one flight?
A flight must have no more than 18 risers and no fewer than 2 under NCC 2022 (D3D14). If your total rise needs more than 18 risers, you must introduce a landing and a change of direction. In a Class 9b building (schools, assembly buildings) up to 36 risers are allowed in consecutive flights if there is a change of direction of at least 30 degrees.
How do I measure total rise correctly?
Measure from the finished floor level at the bottom to the finished floor level at the top - including tiles, carpet or timber flooring. This is the most common mistake. If you measure to the structural floor and then add 20 mm of tiles later, every riser will be short. The calculator includes an optional "top floor finish thickness" field so you can add it in.
What is the ideal riser height for an Australian home?
175 mm is the commonly used ideal in Australian residential construction because it divides neatly into common floor heights (2,800 ÷ 175 = 16 risers) and gives a comfortable 2R + G of about 620 mm with a 270-280 mm going. The calculator defaults to 175 mm but you can change it in Advanced options.
How do I calculate stringer length?
Stringer length = √(total rise² + total run²). For a 2,700 mm rise and 4,200 mm run, that is √(2700² + 4200²) = 5,017 mm. Add 300-400 mm for the top and bottom cut allowances when ordering timber. The calculator shows the exact stringer length for your dimensions.
What is a comfortable stair pitch?
Most Australian residential stairs sit between 30° and 38°. A 32-33° pitch is the sweet spot for comfort. Steeper than 38° feels like a ladder; shallower than 30° takes up too much floor space. The calculator shows the exact pitch angle and flags anything outside the typical range.
Do I need a landing?
A landing is required when a flight exceeds 18 risers, or when the stair changes direction. The landing depth must be at least the stair width. For a straight run under 18 risers, no intermediate landing is required (though the top floor level always acts as a landing).
What is the minimum stair width in Australia?
For a private stairway the minimum width is 600 mm. For a public stairway it is 1,000 mm. These are Deemed-to-Satisfy minimums - practical stairs are usually 900-1,000 mm wide for residential comfort. Wider stairs need intermediate handrails.
Can I use this calculator for deck stairs?
Yes. Deck stairs follow the same NCC rules for riser, going and 2R + G. Enter your deck height as the total rise and your available horizontal distance as the total run. The same compliance checks apply. For external stairs, also check balustrade height (1,000 mm minimum) and the 125 mm sphere gap rule.
Why does my riser need to be constant?
NCC 2022 requires every riser in a flight to be equal within 5 mm, and the largest and smallest riser in a flight to differ by no more than 10 mm. A single short or tall riser is a major trip hazard - people build muscle memory for the stair height and a sudden change causes falls. The calculator distributes the total rise evenly so every riser is identical (or within 1 mm after rounding).
What is the 125 mm sphere rule?
For open-riser stairs, the gap between treads must be small enough that a 125 mm sphere cannot pass through. This prevents small children from falling through and is a NCC 2022 requirement (D3D14). If your design has open risers, check this before construction.
Do state variations affect stair rules?
The NCC is a national code, but each state and territory adopts it with minor variations and additional requirements. For example, NSW has specific variations in the Building Code of Australia, and QLD may require additional fire egress provisions for certain classes. Always confirm with your local certifier or building surveyor - the calculator checks the national Deemed-to-Satisfy limits, which are the baseline in every state.
How do I convert this to imperial measurements?
This calculator is metric-only because Australian construction uses millimetres exclusively. If you need imperial, divide mm by 25.4 to get inches. A 190 mm riser is 7.48 inches; a 240 mm going is 9.45 inches. For a generic imperial stair calculator, use our standard Stair Calculator.
References & Standards
- NCC 2022 Volume One - Building Code of Australia, Part D3 Construction of Exits, Clause D3D14 Goings and Risers
- NCC 2022 Volume Two - Building Code of Australia, Housing Provisions Part 11.2 Stairways and Ramps, Clause 11.2.2
- NCC 2022 Table D3D14 - Riser, going and 2R + G limits by building class
- NCC 2022 Table 11.2.2a - Riser and going dimensions for Class 1 and 10 buildings
- AS 1657 - Fixed platforms, walkways, stairways and ladders - Design, construction and installation
- AS 1428.1 - Design for access and mobility, Part 1: General requirements for access - New building work
- AS 1170.1 - Structural design actions, Part 1: Permanent, imposed and other actions
- ABCB Housing Provisions 2022 - Stairway and ramp provisions