Stair Calculator
Risers, treads and Blondel comfort check
Blondel comfort formula: 2 × riser + going = 630 mm (comfortable between 590 and 650 mm). Always check your local building code.
Summary
| Risers | Riser height | Going | Treads | Angle | Total run |
|---|---|---|---|---|---|
| — | — | — | — | — | — |
About Stair Calculator
The stair calculator works out how many risers and treads a staircase needs from a single measurement: the total rise, finished floor to finished floor. It divides that rise by your target riser height, rounds to a whole number of steps, and reports the exact riser height, going (tread depth), stair angle, and total run.
Comfort is checked with the Blondel formula, the classic rule used by stair builders: two times the riser plus the going should equal about 630 mm, and anything between 590 and 650 mm feels natural to walk. The tool also warns when a riser leaves the common 150–190 mm range or the going drops below 240 mm.
If your landing position is fixed, enter the available run and the calculator derives the going from it instead of from Blondel. Use it for a first stair layout on a house, deck, or basement project — free, live in your browser, with a section drawing that updates as you type. Always confirm the final design against your local building code.
How to use Stair Calculator
- Measure and enter the total rise in millimeters — finished floor to finished floor.
- Optionally enter the available run if the horizontal space is constrained; leave it empty to let the Blondel formula set the going.
- Adjust the target riser height — most residential stairs feel right around 170–180 mm.
- Read the riser count, riser height, going, angle, and total run in the summary.
- Check the Blondel badge and any warnings before finalizing the layout.