Stair calculator
Work out the risers, riser height, going, total going and stringer length for a straight stair, checked against the NCC Housing Provisions.
Measured from finished floor level to finished floor level.
The calculator uses the fewest risers that stay at or under this height.
Level depth of one step, nosing to nosing.
Fixed number of risers
Leave empty to use the maximum riser height.
Stair layout
- Risers
- 1514 treads: the upper floor is the last step
- Riser height
- 180 mm
- Going
- 250 mm
- Total going
- 3,500 mm3.50 m
- Stringer length
- 4,420 mm4.42 m on the diagonal, before the end cuts
- Stair angle
- 35.75°
- 2R + G
- 610 mm
Checked against NCC Housing Provisions 11.2.2 and Table 11.2.2a
- Riser height from 115 mm to 190 mmThis stair: 180 mmPass
- Going from 240 mm to 355 mmThis stair: 250 mmPass
- Slope relationship 2R + G from 550 mm to 700 mmThis stair: 610 mmPass
- From 2 to 18 risers in one flightThis stair: 15Pass
Straight flight only. Riser and going tolerances, headroom, handrails, barriers and landings are not checked, and each state and territory can vary the NCC.
Estimate only. Check product labels and the building rules in your state or territory before you buy or build.
Quick answer
Divide the total rise by the tallest riser you accept and round up to get the number of risers, then divide the total rise by that number for the riser height. A 2,700 mm floor-to-floor height at the NCC maximum of 190 mm needs 15 risers of 180 mm. With 250 mm goings the 14 treads take 3,500 mm of floor, and 2R + G is 610 mm, inside the 550 to 700 mm range.
How to use the stair calculator
- Measure the total rise from finished floor level at the bottom to finished floor level at the top. Add the thickness of any flooring or tiles still to be laid.
- Keep the maximum riser height at 190 mm, the NCC limit in Table 11.2.2a, or lower it for an easier stair. The calculator picks the fewest risers that stay at or under it.
- Set the going: type it, choose Space available and type the length of floor you have, or choose Slope relationship and type a 2R + G target.
- Read the risers, riser height, going, total going, stringer length and angle, then the pass or fail list for riser height, going, 2R + G and risers per flight. Open "Fixed number of risers" to set the number yourself.
How do you calculate stair risers and goings?
Divide the total rise by the tallest riser you accept and round up: that is the fewest risers that keep every step at or under the limit. Then divide the total rise by that whole number to get the riser height, so every riser comes out the same. The NCC treats risers and goings as constant when adjacent ones differ by no more than 5 mm and the largest and smallest in a flight by no more than 10 mm.
A straight stair has one tread fewer than it has risers, because the upper floor is the last step. The total going is the number of treads times the going. The stringer length shown is the diagonal from the foot of the first riser to the edge of the upper floor; the timber you cut it from has to be longer to leave room for the cuts at each end.
risers = total rise ÷ maximum riser height, rounded upriser height = total rise ÷ riserstreads = risers − 1going from the space available = total going available ÷ treadsgoing from the slope relationship = target 2R + G − 2 × riser heighttotal going = treads × goingstringer length = √(total rise² + total going²)stair angle = arctan(riser height ÷ going)What does the NCC say about riser height and going?
The ABCB Housing Provisions set the stair rules for houses in Part 11.2, with headroom in Part 10.3 and handrails and barriers in Part 11.3. NCC 2022 and NCC 2025 give the same figures. The NCC takes legal effect through each state and territory, which can vary it, so check with your council or a building surveyor or certifier, and a qualified builder, before you build.
| Requirement | NCC Housing Provisions |
|---|---|
| Riser height (R), Table 11.2.2a | 115 to 190 mm |
| Going (G), Table 11.2.2a | 240 to 355 mm |
| Slope relationship (2R + G), Table 11.2.2a | 550 to 700 mm |
| Risers in each flight, 11.2.2(1)(a) | 2 to 18 |
| Difference between adjacent risers or goings, 11.2.2(1)(c) | 5 mm or less |
| Largest minus smallest riser or going in a flight, 11.2.2(1)(c) | 10 mm or less |
| Openings in risers, 11.2.2(1)(d) | A 125 mm sphere must not pass between the treads |
| Landing length, 11.2.5 | 750 mm or more |
| Headroom, 10.3.1 | 2.0 m measured vertically above the nosing line |
| Handrail, 11.3.5 | On at least one side, top 865 mm or more above the nosings; not needed where the stair rises less than 1 m |
| Barrier, 11.3.3 and 11.3.4 | Where a person could fall 1 m or more; 865 mm or more above the nosings on a stair |
A stair serving only non-habitable rooms, such as attics and storerooms not used on a regular or daily basis, may use Table 11.2.2b instead: riser 130 to 225 mm, going 215 to 355 mm and 2R + G 540 to 700 mm. The calculator checks Table 11.2.2a only.
How many steps do I need for my floor-to-floor height?
Worked out with a 190 mm maximum riser and 250 mm goings, the values the calculator starts with. Every row passes the four NCC checks: riser height, going, 2R + G and risers per flight.
| Total rise | Risers | Riser height | Treads | Total going | 2R + G |
|---|---|---|---|---|---|
| 600 mm | 4 | 150 mm | 3 | 750 mm | 550 mm |
| 900 mm | 5 | 180 mm | 4 | 1,000 mm | 610 mm |
| 1,000 mm | 6 | 166.7 mm | 5 | 1,250 mm | 583.3 mm |
| 1,200 mm | 7 | 171.4 mm | 6 | 1,500 mm | 592.9 mm |
| 1,500 mm | 8 | 187.5 mm | 7 | 1,750 mm | 625 mm |
| 1,800 mm | 10 | 180 mm | 9 | 2,250 mm | 610 mm |
| 2,400 mm | 13 | 184.6 mm | 12 | 3,000 mm | 619.2 mm |
| 2,600 mm | 14 | 185.7 mm | 13 | 3,250 mm | 621.4 mm |
| 2,700 mm | 15 | 180 mm | 14 | 3,500 mm | 610 mm |
| 2,800 mm | 15 | 186.7 mm | 14 | 3,500 mm | 623.3 mm |
| 3,000 mm | 16 | 187.5 mm | 15 | 3,750 mm | 625 mm |
| 3,400 mm | 18 | 188.9 mm | 17 | 4,250 mm | 627.8 mm |
Riser heights and 2R + G are rounded to 0.1 mm; the calculator shows whole millimetres. At 190 mm, a flight of 18 risers climbs at most 3,420 mm, so a higher total rise needs a landing.
Worked examples
House stair with a 2.7 m floor-to-floor height
The finished floors are 2,700 mm apart. At the 190 mm maximum riser, 2,700 ÷ 190 = 14.21, which rounds up to 15 risers. Each riser is 2,700 ÷ 15 = 180 mm.
With 250 mm goings, the 14 treads take 14 × 250 = 3,500 mm of floor. The stringer diagonal is √(2,700² + 3,500²) = 4,420 mm, or 4.42 m, the stair angle is arctan(180 ÷ 250) = 35.75° and 2R + G is 2 × 180 + 250 = 610 mm. All four NCC checks pass.
Deck stair that has to land within 1.5 m
The top of the decking is 1,100 mm above the paving, and the stair can reach no more than 1,500 mm out from the deck. Type 1100 as the total rise, choose Space available and type 1500. 1,100 ÷ 190 = 5.79 rounds up to 6 risers of 183 mm, and the 5 goings are 1,500 ÷ 5 = 300 mm each.
2R + G is 667 mm, the stair angle is 31.43° and the stringer diagonal is 1,860 mm, so all four checks pass. Because this stair rises 1 m or more, the NCC needs a handrail on at least one side with its top at least 865 mm above the nosings, and a barrier wherever someone could fall 1 m or more.
Why measure the total rise between finished floor levels?
Because flooring changes only the top or bottom riser, and the NCC lets adjacent risers differ by no more than 5 mm. A stair laid out between bare slabs fails that limit if 20 mm of tiles later go on the upper floor and nothing goes on the lower one: the top riser ends up 20 mm taller than the rest, which also breaks the 10 mm limit for the whole flight.
Measure from finished floor level to finished floor level, or add the planned flooring thickness before you type the total rise. For a deck, measure from the top of the decking down to the surface the stair will land on.
Common questions
What is the maximum riser height for stairs in Australia?
The maximum riser height is 190 mm and the minimum is 115 mm under Table 11.2.2a of the NCC Housing Provisions, with goings from 240 to 355 mm and 2R + G from 550 to 700 mm. NCC 2022 and NCC 2025 give the same figures. A stair serving only non-habitable rooms that are not used daily may have risers up to 225 mm under Table 11.2.2b.
How many steps do I need for a 2.7 m floor-to-floor height?
A 2.7 m (2,700 mm) rise needs 15 risers of 180 mm at the 190 mm maximum: 2,700 ÷ 190 = 14.21 rounds up to 15. The stair has 14 treads, because the upper floor is the last step, so with 250 mm goings it takes 3,500 mm of floor. Its 2R + G is 610 mm, inside the NCC range.
How many steps can a stair have before a landing?
A flight can have no more than 18 risers and no fewer than 2 under clause 11.2.2 of the NCC Housing Provisions. At the 190 mm maximum riser height, 18 risers climb at most 3,420 mm, so a higher rise needs a landing. A landing must be at least 750 mm long, measured 500 mm in from the inside edge where the stair changes direction.
Do stairs need a handrail in Australia?
Yes, once the stair rises 1 m or more: the NCC Housing Provisions require a handrail along at least one side of the flight, with its top at least 865 mm above the stair nosings. A stairway with a change in elevation of less than 1 m is exempt. A barrier is also needed wherever a person could fall 1 m or more.
How much headroom do stairs need?
A stair needs at least 2.0 m of height measured vertically above the nosing line of the treads, under clause 10.3.1 of the NCC Housing Provisions, and the same 2.0 m above landings. The calculator does not check headroom, so measure the opening above the stair separately, including any beam or bulkhead it passes under.
Can stairs have open risers in Australia?
Yes, as long as the openings do not let a 125 mm sphere pass through between the treads, under clause 11.2.2 of the NCC Housing Provisions. Barrier and balustrade openings have the same 125 mm limit, measured above the nosing line on a stair. A stair serving only non-habitable rooms that are not used daily does not have to meet the riser opening rule.
Sources
- Australian Building Codes Board, NCC 2025 Housing Provisions, Part 11.2 Stairway and ramp construction (checked 19 October 2026)2 to 18 risers per flight; Table 11.2.2a riser 115 to 190 mm, going 240 to 355 mm, 2R + G 550 to 700 mm; 5 mm and 10 mm tolerances; 125 mm openings; Table 11.2.2b; 750 mm landings.
- Australian Building Codes Board, NCC 2022 Housing Provisions, Part 11.2 Stairway and ramp construction (checked 19 October 2026)The same stair figures in the earlier edition.
- Australian Building Codes Board, NCC 2025 Housing Provisions, Part 10.3 Room heights (checked 19 October 2026)10.3.1(1)(f): 2.0 m above the nosing line of stairway treads and above landings. NCC 2022 Part 10.3 gives the same height.
- Australian Building Codes Board, NCC 2025 Housing Provisions, Part 11.3 Barriers and handrails (checked 19 October 2026)Barriers where a fall is 1 m or more, 865 mm on stairs, 125 mm openings; handrail on at least one side, 865 mm high, not needed below 1 m of rise. NCC 2022 Part 11.3 gives the same figures.
- Australian Building Codes Board, General NCC FAQ (checked 19 October 2026)The NCC is given legal effect through adoption by each state and territory, which can vary it.
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