Work out the number of risers, riser height, tread depth, stair length and angle for a straight staircase.
The horizontal depth from one step's nosing to the next.
Hover over a riser to see the dimensions for that exact step.
Embed on your website →Each alternative uses its own recommended tread depth (the 620 mm stair formula), not necessarily the tread depth you chose above.
Click a row to use that alternative in the calculator above.
| Risers | Riser height | Recommended tread | Length | Angle |
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This calculator applies only to a straight staircase with a single continuous flight — not spiral staircases, turned staircases or staircases with landings. The result is a guide only and no substitute for proper structural design.
A common rule of thumb for a comfortable staircase is that 2 × riser height + tread depth ≈ 620 mm. Norway's TEK17 building code guidance sets 620 mm ± 20 mm as a pre-accepted performance level for the ratio between riser height and tread depth, measured along the walking line. This is a Norwegian building-code requirement — other countries have their own rules and typically use a similar but not identical rule of thumb (often called Blondel's formula internationally), so always check the building code that applies where you live.
The calculator suggests a number of risers based on a practical riser height of around 175 mm. With, say, 2,800 mm of height difference, that gives 2800 ÷ 16 ≈ 175 mm per riser. You can always adjust the number yourself — fewer risers give a taller, steeper staircase, more risers give a lower, gentler one.
The total horizontal length depends heavily on the tread depth and the number of treads — a staircase with many, deep treads takes up much more floor space than a steep staircase with few, shallow treads. Use "More options" if you have a fixed available length to work within.
The calculator uses roughly 175 mm as a practical starting point, but the right design must be assessed together with tread depth, staircase type and applicable requirements.
The horizontal distance between two consecutive step noses.
2 × riser height + tread depth ≈ 620 mm — a well-known measure of a comfortable staircase, used as a pre-accepted performance level in Norway's TEK17 guidance.
Normally 15, when the floor at the top serves as the final level.
Tread depth × number of treads.
Arctan(total height ÷ total horizontal length).
Use the Pythagorean theorem: √(height² + horizontal length²). This is the geometric length from the start to the end of the staircase flight, and doesn't include extra material for cutting, fastening or other construction details.
No. The result is a guide only. Applicable building codes and other structural requirements must be checked for the specific staircase.