Stair Calculator
Enter the total rise of your staircase and the step height you want — the calculator returns the number of steps and the exact riser height that keeps every step equal.
Steps and height at once
Enter the total rise and your target step height and the calculator returns the whole number of steps and the actual riser height together.
Aim for 17–19 cm
Comfortable stairs use risers of roughly 17–19 cm; rounding to whole steps keeps every riser identical, which is what matters most for safety.
What does a stair calculator do?
From total rise to equal steps
A stair calculator turns the height a staircase must climb into a clean, buildable layout. You measure the total rise — the vertical distance from one finished floor to the next — and choose the step height you would like each riser to be. Because you cannot build a fraction of a step, the calculator divides the rise by your target height and rounds to the nearest whole number of steps, then shares the rise evenly across them so every riser comes out exactly the same. That equal-riser result is the number that decides whether a flight feels comfortable underfoot or becomes a trip hazard.
Enter the total rise in centimetres and a target step height, and the calculator returns the number of steps and the exact equal riser height instantly.
The number of steps is the total rise divided by your target step height, rounded to a whole number, and the actual step height is the rise divided by that step count.
steps = round(rise ÷ target height)You cannot build 15.56 steps, so the count rounds to 16. Dividing the 280 cm rise by 16 gives an actual riser of 17.5 cm — close to your 18 cm target and identical for every step. Rounding the count down would instead give taller steps, while rounding up gives shorter ones; either way, splitting the rise evenly is what keeps the flight regular.
Suppose your floor-to-floor height is 280 cm and you would like steps of about 18 cm.
Divide the rise by the target
280 ÷ 18 = 15.56 — the ideal but impossible number of steps.
Round to whole steps
round(15.56) = 16 — you can only build a whole number of steps.
Split the rise evenly
280 ÷ 16 = 17.5 cm — the actual riser height, identical for every step.
The two outputs work together. The number of steps (16 in the example) tells you how many treads to build, and the actual step height (17.5 cm) tells you exactly how tall each riser must be. The key idea is that rounding the step count forces a small adjustment to the height: because 16 steps fit the 280 cm rise better than the 15.56 the target implied, each riser shrinks slightly from 18 cm to 17.5 cm. That trade is worth it, because every step ending up the same height is what makes a staircase feel safe — an uneven riser, even by a centimetre, is the single most common cause of stair stumbles. A comfortable range for most homes is roughly 17–19 cm per riser; if your actual step height lands far outside that, adjust the target height and recalculate until the equal riser sits in a comfortable band.
The math is exact, but a real staircase has more to it than the riser height alone.
Riser only — check your local building code
This calculator sizes the riser height and step count only; it does not size the tread depth (the going), the overall run, or the headroom, all of which a full staircase design needs. Step dimensions are also regulated: building codes set limits on minimum and maximum riser heights and on the relationship between riser and tread. Treat the result as a planning starting point and confirm the final dimensions against the building code that applies where you live before you cut any timber.