Staircase Calculator
Calculate staircase dimensions and ergonomics
How the calculation works
Enter the height the stairs must climb and, optionally, the number of steps or tread depth. The calculator determines the number of risers, riser height h and tread depth b using the Blondel rule and checks the recommended ranges.
Formula and assumptions
Number of risers N ≈ H ÷ ideal riser height (about 17.5 cm), rounded to a whole number; riser height h = H ÷ N. Blondel rule: 2h + b ≈ 60–66 cm. Recommendations in the app: h 15–19 cm, b 24–32 cm. For straight stairs the number of treads is N − 1. Stair rules and regulations differ by country and building use.
Worked example
Floor-to-floor height H = 280 cm: N = 280 ÷ 17.5 = 16 risers, h = 280 ÷ 16 = 17.5 cm. For 2h + b = 63 cm: b = 63 − 35 = 28 cm. Treads 16 − 1 = 15, horizontal run 15 × 28 = 420 cm.
What affects real consumption
- Floor finishes change the real height of the first and last step.
- The available length for the stair and headroom.
- Stair and safety regulations for the type of building.
Frequently asked questions
What is the Blondel rule?
An empirical formula 2h + b ≈ 60–66 cm linking riser height and tread depth so that walking is comfortable and safe.
Does the calculator replace a stair design?
No – it gives indicative dimensions; final dimensions and compliance with regulations must be confirmed by the designer.