Stair Calculator Australia — Rise, Going & NCC ComplianceNCC
Stair dimensions
Measure vertically from finished floor level to finished floor level.
NCC minimum: 240 mm · Comfortable residential: 270–320 mm
NCC minimum for a private stair: 600 mm · Comfortable: 900–1000 mm
Typical: 19 mm (DAR pine), 32 mm (hardwood), 42 mm (feature hardwood)
Stair layout
Dimensions per step
Overall stair geometry
Timber required
✓ NCC Compliant
⚠ NCC Issues Found
This Australian stair calculator works out the number of risers, actual riser height, going (tread depth), total run, stringer length, and pitch angle for any staircase. It performs a live NCC (National Construction Code) compliance check against the key dimensional limits for private residential stairs: maximum riser height 190 mm, minimum going 240 mm, minimum stair width 600 mm, and the 2R+G comfort formula (target range 550–700 mm). The calculator divides your total rise evenly across the minimum number of steps required to stay within the 190 mm riser limit, then reports the actual riser height and flags any non-compliance clearly.
Frequently Asked Questions
What is the maximum riser height for stairs in Australia under the NCC?
The National Construction Code (NCC) Volume 2, Part 3.9.1 sets the maximum riser height for a private stairway (in a house) at 190 mm. The minimum riser height is 115 mm. These limits apply to all habitable building work in Australia. Commercial stairs (NCC Volume 1) follow similar but slightly different limits under AS 1657.
What is the minimum going (tread depth) for stairs in Australia?
The NCC specifies a minimum going of 240 mm for private residential stairs. The going is measured horizontally from the front edge (nosing) of one tread to the front edge of the next. A going of 270–300 mm is considered comfortable for most adults. Shallower goings force you to descend side-on and increase the risk of falls.
What is the 2R+G stair comfort formula?
The 2R+G formula — where R is the riser height and G is the going in millimetres — is an ergonomic guideline for comfortable stair proportions. A result between 550 mm and 700 mm is considered comfortable, with 600–650 mm being ideal. This formula originated in 17th-century French stair design and is widely referenced by Australian stair builders, although the NCC does not mandate a specific 2R+G value.
How do I measure total rise for a staircase?
Total rise is the vertical distance from finished floor level at the bottom of the stairs to finished floor level at the top. Measure this after floor finishes (tiles, floorboards, carpet) are in place, or calculate finished heights from your structural drawings. Getting this measurement wrong by even 5–10 mm results in inconsistent riser heights, which is a tripping hazard and an NCC non-compliance.
Do stairs require a handrail in Australia?
Under NCC Volume 2, a handrail is required on any stairway with 2 or more risers in a residential building. The handrail must be between 865 mm and 1000 mm above the nosing of each tread, and must be continuous from the top to the bottom riser. Balustrades are required where the floor level is more than 1 m above ground or the floor below.
How to use this calculator
- Enter the total rise in millimetres — the vertical distance from finished floor level at the bottom to finished floor level at the top. Measure after all floor finishes are in place, or calculate from structural drawings using finished floor heights.
- Enter your preferred going (tread depth) in mm. The NCC minimum is 240 mm; a comfortable residential going is 270–300 mm. Enter the going you want, and the calculator will verify it meets NCC requirements.
- Enter stair width in mm. NCC minimum for a private stair is 600 mm; comfortable is 900–1000 mm for a main internal staircase.
- Enter the tread thickness — the thickness of each tread board (nosing). Common: 19 mm (pine), 32 mm (hardwood).
- Click Calculate. Results show the number of risers, actual riser height, total run, stringer length, pitch angle, and a full NCC compliance check.
Worked example: Total rise 2,700 mm, preferred going 280 mm, width 900 mm. Risers: ceil(2700 ÷ 190) = 15 risers. Actual riser height: 2700 ÷ 15 = 180 mm. Going: 280 mm. 2R+G: 2×180 + 280 = 640 mm (comfortable range 550–700 mm ✓). Total run: 14 treads × 280 mm = 3,920 mm. Stringer length: √(3.92² + 2.7²) ≈ 4.75 m. NCC check: riser 180 mm ≤ 190 mm max ✓, going 280 mm ≥ 240 mm min ✓, width 900 mm ≥ 600 mm min ✓.
Understanding your results
The number of risers is determined by dividing the total rise by the maximum allowed riser height (190 mm) and rounding up — this ensures every riser is within the NCC limit. The actual riser height is then the total rise divided evenly across all risers. All risers must be the same height within 5 mm tolerance — uneven risers are a tripping hazard and an NCC non-compliance.
The stringer length is the diagonal measurement of the staircase and tells you the minimum length of stringer board to purchase. Order stringer timber at least 100 mm longer than the calculated length to allow for the birdsmouth cut at the top and the foot cut at the bottom. Common stringer sizes for residential stairs are 250×50 mm or 300×50 mm F17 LVL or solid hardwood.
Common mistakes: Measuring total rise before floor finishes are in place — tile, timber, or carpet thickness can add 10–20 mm and change the riser calculation; calculating treads = risers (there is always one fewer tread than risers); and setting handrail height from the floor instead of from the tread nosing — the NCC measures handrail height from the nosing of each tread.
Stair design and construction in Australia
Stairs are one of the most regulated elements in Australian residential construction because they are one of the most common causes of falls. Understanding the NCC requirements and the principles behind them helps you design stairs that are both compliant and genuinely comfortable to use.
The 2R+G formula: The 2R+G formula (where R = riser height and G = going) is an ergonomic guideline derived from human gait — a step with a higher riser can be comfortable if the going is shorter, and vice versa. The ideal range of 550–700 mm reflects the natural stride length of an adult at a comfortable pace. The NCC doesn't mandate a specific 2R+G value, but building certifiers and experienced builders use it as a quality check. A 2R+G below 550 mm produces steep, tiring stairs; above 700 mm produces shallow stairs that feel awkward.
NCC requirements summary: For a private stairway in a Class 1 building (house): maximum riser 190 mm, minimum riser 115 mm, minimum going 240 mm, minimum width 600 mm, all risers within 5 mm of each other, handrail required for 2+ risers at 865–1000 mm above nosing, balustrade required where stair is more than 1 m above ground or floor below.
Common Australian stair configurations: Straight single-flight stairs (the most common), with landings required if total rise exceeds 4,200 mm in a single flight (NCC Volume 2). Dog-leg stairs (two parallel flights connected by a landing) and L-shaped stairs are common for split-level homes. Spiral stairs are permitted with stricter requirements and are typically limited to secondary access only.
Timber stair materials: Most Australian residential stairs use 300×50 mm F17 LVL stringers with 90×19 mm or 140×19 mm hardwood treads (spotted gum, blackbutt, Tasmanian oak) for a feature appearance. Treated pine treads are used for external stairs. For a building permit, timber stairs must comply with AS 1684 or be certified by a structural engineer.
Australian standards and references
- NCC Volume 2 (Building Code of Australia) Part 3.9.1 — Private Stairways: sets all mandatory dimensional limits for residential stairs including maximum riser (190 mm), minimum going (240 mm), handrail height (865–1000 mm), and balustrade requirements.
- AS 1657:2018 — Fixed Platforms, Walkways, Stairways and Ladders: applies to commercial and industrial stair design (not residential private stairs).
- AS 1684.2:2010 — Residential Timber-Framed Construction: stringer size and span requirements for timber stairs.
- NCC Volume 2 Part 3.9.2 — Balustrades and Handrails: sphere rule (125 mm for private, 100 mm for some locations), handrail graspability requirements.