Stair calculator
Design stairs of any kind — straight, L or U with a landing or winders, spiral: the rise is split into equal risers close to the height you prefer, the tread follows from the step formula 2h + t ≈ 630 mm, and the stairs are checked against the usual comfort and code limits.
You need
16 steps
175 mm × 280 mm · riser × tread · 32.0°
- Flight length
- 4.20 m
- Stringer
- 5.05 m
- 2h + t = 630 mm
- Comfortable
- Risers near 180 mm2.80 ÷ 0.180 = 15.6 → 16; 2.80 ÷ 16 = 175 mm
- Tread from 2h + t = 630 mm630 − 2 × 175 = 280 mm
- Flight length, angle and stringer15 × 280 = 4.20 m; 32.0°; 5.05 m
The calculator gives an estimate by the usual norms. Consumption depends on the product and the surface: check the manufacturer’s data before you buy.
How it’s calculated
- 1
Number of risers = floor-to-floor height ÷ preferred riser, rounded to the nearest whole number.
- 2
Real riser = height ÷ number of risers — all risers equal.
- 3
Tread = step formula − 2 × riser (2h + t ≈ 630 mm fits the human stride).
- 4
Treads = risers − 1; flight length = treads × tread.
- 5
Angle = arctan(riser ÷ tread); stringer = √(height² + flight length²).
Worked example
A straight flight for a floor-to-floor height of 2.8 m:
The input
- Kind of stairs
- Straight
- Floor to floor, m
- 2.8
- Preferred riser, mm
- 180
- Flight width, m
- 0.9
The result
16 steps
175 mm × 280 mm · riser × tread · 32.0°
- Flight length: 4.20 m
- Stringer: 5.05 m
- 2h + t = 630 mm: Comfortable
The calculation
- Risers near 180 mm2.80 ÷ 0.180 = 15.6 → 16; 2.80 ÷ 16 = 175 mm
- Tread from 2h + t = 630 mm630 − 2 × 175 = 280 mm
- Flight length, angle and stringer15 × 280 = 4.20 m; 32.0°; 5.05 m
How many steps for a 2.8 m height?
With a preferred riser of 170 mm, 2.8 m gives 16.47, rounded to 16 risers of 175 mm. The tread is 630 − 2 × 175 = 280 mm, 15 treads make a 4.2 m flight, and the angle is 32° — a comfortable staircase.
What makes a staircase comfortable?
A riser of 150–180 mm, a tread of 250–320 mm and an angle of 30–40°. The formula 2h + t = 600–640 mm keeps the step natural. Building codes set the highest riser and the shortest tread; the calculator warns when a flight goes beyond them.
Questions
Why must all risers be equal?
The foot remembers the step height after the first two steps; one riser different by a centimetre makes people trip. That is why the height is split into equal parts.
Is the floor finish included?
Measure from finished floor to finished floor. If the finishes aren’t laid yet, add their thickness to the measurement.
What if the flight is too long for the room?
Choose a higher riser (within the code), or split the flight with a landing or a turn: the risers and treads stay the same.
The same calculator in the Kvadrino app
Kvadrino for Android works offline: enter the room once and get tiles, paint, flooring and an estimate for the client. The app is in closed testing — write to us and we will add you as a tester.
Coming soon to Google Play