Deck Stair Calculator

115–190Riser (mm)

240–355Going (mm)

550–7002R + G (mm)

Total riseground or landing → top of the decking (mm) Goingtread depth you want (mm) Tread thicknessto cut off the stringer bottom (mm)

Marking out the stringer

Set the framing square at the riser on one arm and the going on the other; mark every step the same.
Cut the bottom of the stringer down by the tread thickness, so the first step isn't taller than the rest.
Next-step difference no more than 5 mm, whole flight no more than 10 mm.
Measure to the finished surfaces. Check balustrade and handrail where the code needs them.

Let DeckMate do the whole deckDraw the deck, set the height — it works out the stairs, the stringers and the frame, and prices them. deckmate.com.au →

Rules: National Construction Code, ABCB Housing Provisions Part 11.2.2, Table 11.2.2a (non-spiral stairs) and its 5 mm / 10 mm tolerances. Check the edition your building surveyor uses (NCC 2025 applies in Victoria from 1 May 2026). General information only — not engineering or certification advice.