Staircase calculator
Step count, riser, Blondel value, angle and floor run.
Result
Indicative calculation, run in your browser. No data is sent anywhere.
A comfortable staircase respects a simple relation between riser and going, known as the Blondel rule: twice the riser plus the going should land around 60 to 64 cm. Outside that range the climb becomes tiring or the descent unsafe.
The calculator starts from the floor height, looks for a step count that puts Blondel in the right range, then returns the exact riser, the flight angle and the horizontal run. That run is usually what decides whether the stair fits the available opening.
You can also let the plan supply these figures for you.
Plan measurementFrequently asked questions
What does the Blondel value mean?
It is twice the riser plus the going. Between 58 and 64 cm the stair is comfortable; below that it becomes flat and space-hungry, above it becomes steep. The tick means you are inside the range.
Does the calculation account for the opening?
The opening length serves as a reference: compare it with the floor run returned by the calculation. If the run exceeds it, you have to reduce the going, accept a steeper stair, or move to a turning staircase.
Is this compliant with standards?
It is a comfort and footprint calculation, not a regulatory check. Headroom, guardrails, widths and accessibility rules depend on the country and the building use, and still have to be verified.