Free Stair Calculator — Treads & Risers to the Current NCC

Design compliant stair geometry for an Australian home. Enter your total rise and the calculator works out the number of risers, riser height, going (tread depth) and stair angle — then checks every dimension against the current NCC (2022 Housing Provisions) limits for Class 1 homes, with clear pass/warning results and the nearest compliant option if something's out.

How to use this calculator

Measure and enter your total rise — the vertical height from finished floor to finished floor.
Optionally enter a preferred riser height (170–185 mm is typical for a comfortable domestic stair) and any limit on your available run.
Review the results: number of risers, riser height, going, total run and stair angle.
Check the NCC geometry check panel — every dimension gets a clear pass or warning, and if a result falls outside the limits, the calculator shows the nearest compliant option.

What this calculator checks (NCC 2022 Housing Provisions, Class 1 homes)

Riser height: 115–190 mm
Going (tread depth): 240–355 mm
Slope relationship (2R + G): 550–700 mm
Risers per flight: no more than 18 (more requires a landing)
Consistency: all risers equal and all goings equal within NCC tolerance (max 5 mm between adjacent steps, 10 mm across the flight)

A comfortable domestic stair typically sits around a 175–180 mm riser with a 250–280 mm going, with 2R + G near 620 mm.

Important:

This calculator applies the dimensional limits for stairs in Class 1 buildings (houses) under the current NCC Housing Provisions. It's a design and planning aid — not a substitute for your approved plans or professional certification. Stair construction, balustrades, handrails, headroom and landings have additional requirements, and your building surveyor has the final say. Always confirm your stair design against your approved documentation before building.

Frequently Asked Questions (F&Q)

FAQ 1
Question: What is the maximum riser height in Australia?
Answer: For Class 1 homes under the current NCC, risers must be between 115 mm and 190 mm, and every riser in the flight must be equal. This calculator checks both automatically.

FAQ 2
Question: What is "going" on a stair?
Answer: The going is the horizontal depth of each tread from nosing to nosing — effectively how much foot room each step gives you. The NCC requires 240–355 mm for houses.

FAQ 3
Question: What is the 2R + G rule?
Answer: It's the NCC's comfort formula: twice the riser height plus the going must fall between 550 mm and 700 mm. It keeps the relationship between step height and depth in a range people can walk naturally. Around 620 mm is the sweet spot for most domestic stairs.

FAQ 4
Question: How many steps before I need a landing?
Answer: A single flight can't have more than 18 risers under the NCC. Beyond that you need a landing — which also adds to the total run you need to allow in your floor plan.

FAQ 5
Question: How do I measure total rise accurately?
Answer: Measure vertically from finished floor level to finished floor level — including floor coverings if they differ between levels. Even a 20 mm error in total rise changes every riser in the flight, so measure twice.

FAQ 6
Question: Can I rely on this calculator for my building approval?
Answer: Use it to get your geometry right early — but your approved plans and your building surveyor are the authority. Site conditions, headroom, handrails and balustrades all affect the final design.