Stair Calculator
Work out the number of steps, riser height, tread going, total run, and stringer length from your floor-to-floor rise. Free, instant, no sign-up.
Staircase
A comfortable stair keeps risers 150–200 mm and the going 250–320 mm. Always check your local building regulations for the exact limits.
Your staircase
Number of steps (risers)15
Actual riser height180,0 mm ✓
Number of treads14
Total run (going ✓)3,50 m
Stringer length (min)4,42 m
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Create a free account →How the stair calculation works
risers = round(total rise ÷ target riser) riser height = total rise ÷ risers treads = risers − 1 total run = treads × going stringer = √(total rise² + total run²)
FAQ
- How do I calculate the number of stairs?
- Divide the total floor-to-floor rise by your target riser height and round to the nearest whole number — that is the number of risers (steps). The actual riser height is the total rise divided by that number. This calculator also gives treads, run, and stringer length.
- What is a comfortable riser height and tread depth?
- A comfortable stair keeps risers between 150–200 mm and the going (tread depth) between 250–320 mm. The calculator flags whether your numbers fall in range.
- How do I calculate stair stringer length?
- The minimum stringer length is the diagonal: the square root of (total rise² + total run²). Add extra for the top and bottom connections and any overhang.
- Do stairs have to meet building regulations?
- Yes — riser, going, headroom, and pitch limits are set by local building regulations. Use this as a design starting point and confirm against your code. Create a free BuilderBuddi account to quote the job.
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