Stair Calculator Australia: Rise, Going, Stringer Length and NCC Checks
A site workflow for Australian stairs: measure finished rise, pick going and riser count, check NCC geometry, then cut stringers once.
This guide is written for Australian tradies and focuses on practical, metric-first workflows you can apply on site.
Metric units are used throughout with Australian standards context where applicable.
Use these calculators with this guide
Apply the steps from this article directly in the matching tools.
Move from this guide into calculators, then into the TradeSet app
TradeSet connects practical guides to calculators so you can apply the method, keep results in history, and manage everything in one app.
- Guide
- Calculator
- TradeSet app
What an Australian stair calculator should give you
On site you need four numbers before you cut a stringer: riser height, going (run per tread), total run, and stringer length. A stair calculator Australia search is usually someone with a tape on a void, not someone writing a spec. Get finished floor to finished floor first, then test riser counts until rise and going both feel right and fit the opening.
NCC Volume Two sets geometry limits for most Class 1 buildings. Those limits change with the edition and the stair type (private vs public). Treat calculator output as planning, then confirm the current NCC clause and the approved drawings before you fabricate.
Measure total rise from finished levels
Total rise is finished lower floor to finished upper floor, including tiles, timber, or carpet that is not down yet. Rough structural levels will push every riser out once finishes go on. On reno work, measure at more than one point and use the controlling (largest) rise.
Keep every input in millimetres. Mixed metres and millimetres is the fastest way to recut a stringer.
NCC rise, going, and 2R+G — what to check
For most houses, NCC Volume Two is the document. You are checking three things together: maximum riser, minimum going, and the 2R+G comfort band (two risers plus one going). Public stairs and commercial work sit in different NCC volumes and often tighter limits.
Do not memorise a single millimetre figure from a blog. Open the current NCC edition for the occupancy, then run the same numbers in a calculator so you can see which riser count still passes. TradeSet’s stairs tool does that geometry check on device; Pro unlocks the NCC pass/fail line on the result.
- Riser: all risers equal, within the max for that stair type.
- Going: all goings equal, not under the minimum for that stair type.
- 2R+G: two risers plus one going inside the NCC range for that stair.
- Headroom and width are separate checks — geometry alone is not a certificate.
Stringer length from rise and going
Total run is going × number of goings (usually one less than the number of risers for a straight flight). Stringer length is the hypotenuse: square root of (total rise² + total run²). That is the line along the pitch, not the timber you buy — add for landings, treads, and waste.
If the opening is out of square, perfect 2R+G still fits badly. Check diagonals with a square or 3-4-5 before you commit to the cut.
Common recuts on Australian sites
The usual failures are: rise taken off joists not finished floor, going squeezed to fit a tight void without re-checking 2R+G, and one stringer cut from a different datum than the other. Changing the nosing or finish after the stringers are cut is the other classic.
Lock the geometry in writing (or in the app) before anyone picks up the saw. If the architect changes the void, re-run rise and going — do not scale an old stringer.
Run it in the TradeSet stairs calculator
The TradeSet stairs calculator is built for millimetre site work: total rise in, riser count and going out, stringer length on the same screen. In the iOS app you can reopen the last calc and, on Pro, check NCC geometry without a laptop.
Use Stairs with Check Square when the frame is suspect. Outputs are general guidance. Final stairs still follow approved plans, the current NCC, and the certifier.