Stair calculator
Design a comfortable staircase from the floor-to-floor height using the Blondel rule.
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How it is calculated
steps = total rise / riser height
tread = 63 − 2 × riser (Blondel rule, cm)
The Blondel rule links stair geometry to the human stride: two risers plus one tread should total 62–64 cm (24–25 in).
Frequently asked questions
How many steps for a 9 ft (274 cm) rise?
With about 7 in (17.5 cm) risers, 16 risers and treads of about 11 in (28 cm).
What does the IRC require?
In US homes: riser up to 7¾ in and tread at least 10 in.