What stair geometry does this calculate?
This calculator models one straight floor-to-floor flight. It selects a whole riser count from the entered maximum, treats the upper floor as the top landing, and reports transparent geometry and configurable checks.
How to use the Stair Calculator
- Step 1Enter finished-floor total rise, riser target and tread going.
- Step 2Optionally provide available run, measured headroom and custom minimums.
- Step 3Review the exact riser/tread distinction and proportional side elevation.
Formula / How it works
Actual riser = total rise ÷ whole riser count; treads = risers − 1; run = treads × going.
Example
A 2800 mm rise at 175 mm gives 16 risers, 15 treads and a 3750 mm run at 250 mm going.
Stair Calculator FAQ
Why are there fewer treads than risers?
For the modelled floor-to-floor flight, the upper floor acts as the top landing, so the flight has one fewer tread than risers.
Is the stringer result a board cutting length?
No. It is the theoretical inclined slope and excludes extensions, connections, tread thickness and construction details.
Does a passing result prove code compliance?
No. The tool provides geometry and user-entered dimensional checks only; complete local regulatory and structural review remains necessary.