DIY Timber Stairs · Free planning tool
Timber stair calculator
Estimate the number of risers and treads, individual riser height and horizontal projection for a straight timber stair. Enter your finished floor-to-floor height and choose an indicative going. Use the drawing as a starting point for an enquiry.
Planning estimate only. This tool does not assess building compliance, structural design, landings, headroom, barriers, nosings or site conditions. The 140–190 mm riser range is a calculator planning range, not a statement of legal compliance. Have the final stair design checked before ordering or building.
The calculator
Going is the horizontal spacing between consecutive nosings. It can differ from the board depth. These are geometry examples, not confirmation of a product profile. The historical 290 mm board drawing shows 280 mm going; confirm your ordered profile separately.
How the stair calculation works
The total rise is divided by the number of risers. Where the upper landing forms the last step, the number of separate treads is one less than the number of risers. Horizontal projection equals the number of treads multiplied by the going.
Example: a 3,000 mm total rise with 17 risers gives 16 treads and approximately 176.5 mm per riser. At a 240 mm going the estimated projection is 3,840 mm. The drawing does not include tread thickness or nosing detail.
What should I measure?
Measure vertically from the finished lower surface to the finished upper landing. Also measure the width across the flight and the horizontal space available. Do not measure the diagonal distance as the total rise.
Discuss your timber stair kit
Browse timber stair kits or discuss internal stairs. For help confirming a stair layout, call 03 9720 7266 or send your measurements.