Free tool · House stairs
Stair calculator
Enter the height your stairs have to climb. The calculator works out the number of steps, the exact riser and the tread depth, and checks them against the National Construction Code.
Your measurements
The set-out updates as you type.
The height from the surface the stairs land on to the top of the deck, verandah or landing.
The code allows 115 mm to 190 mm. The calculator uses the closest height that divides the rise evenly.
Called the going: 240 mm to 355 mm, measured from the front of one tread to the front of the next.
For stairs on a house under the National Construction Code 2022. It sets out the steps. It does not size stringers, posts or footings, and it does not replace a building certifier.
Your set-out
- Risers
- 8each 175 mm high
- Treads
- 7each 250 mm deep
- Total run
- 1,750mmalong the ground
- Slope check
- 600mmmust be 550 to 700
- These stairs rise 1 m or more, so they need a handrail at least 865 mm above the tread nosings, and a balustrade wherever the fall is 1 m or more.
- Every riser must match its neighbour within 5 mm.
How the calculator works
It divides the total rise into equal risers, picks the tread depth closest to the one you asked for, and keeps every figure inside the limits the National Construction Code housing provisions set for stairs on a house:
- Risers between 115 mm and 190 mm
- Goings between 240 mm and 355 mm
- Twice the riser plus the going between 550 mm and 700 mm
- No more than 18 risers in a flight
- Landings at least 750 mm long between flights
How to measure the total rise
Measure straight down from the top of the deck, verandah or landing to the surface the bottom step will sit on. If the ground slopes, measure to the spot where the stairs will land, not to the ground under the deck edge. Allow for any paving or slab that is still to be laid.
What the numbers do not cover
- Stringer, post and footing sizes, which come from span tables or an engineer
- The handrail and balustrade, which have their own rules
- Whether your job needs building approval, which our approval guide answers job by job
Our guide to building external timber stairs covers all three. If you would rather have the stairs measured and built, see our external stairs service.
Straight answers
Stair set-out questions.
How many steps do I need?
Divide the total rise by a riser between 115 mm and 190 mm and round to a whole number. A 1,400 mm rise works out to 8 risers of 175 mm, which needs 7 treads.
What is the 2R + G rule?
Twice the riser plus the going must add up to between 550 mm and 700 mm. It stops steep stairs having shallow treads, and keeps the stride comfortable from top to bottom.
When do stairs need a landing?
A flight can have no more than 18 risers. Taller stairs are split into flights, with a landing at least 750 mm long between them.
Does it work for stairs inside the house?
Yes. The National Construction Code sets the same riser, going and slope limits for stairs inside and outside a house. It does not cover spiral stairs, or stairs in commercial buildings, which have their own rules.
Get a quote
Rather have them built?
A call or an email books a walk-through. Ben measures the rise on site, sets the flight out to the code and gives you a clear written quote.
- Phone
- 0430 705 916
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Fri and Sat 6:30am to 4:30pm
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- QBCC 15357497