Stair Calculator
Calculate basic straight-stair geometry: risers, treads, and horizontal run.
Straight-stair geometry
Simple mode uses a 17.5 cm reference riser, rounds the riser count, and recalculates actual rise and tread from 2R + T = 63 cm. Custom mode keeps the target riser and tread you enter.
Actual riser = total rise ÷ riser count
A reference, not structural design
The 2R + T expression is shown as a geometric reference. Comfort, landings, width, guards, and permitted limits depend on local code and project requirements.
Frequently asked questions
How many treads are there?
In this straight-stair model there is one fewer tread than risers.
Is 2R + T a building code?
Not by itself. It is a reference that must be checked against applicable requirements.
Does it design the structure?
No. It only calculates basic geometry.
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