Stairs Calculator
Calculate straight stairs to second floor: step count, riser height, tread depth, slope angle. Drawing based on building codes.
Distance from finished first floor to finished second floor
Horizontal projection of the flight on the floor
Desired tread depth, recommended 25–30 cm
Desired riser height, recommended 15–20 cm
Stairs drawing (side view)
Schematic side-view drawing to scale. Lines show step proportions and slope angle.
Calculation Formula
n = ⌊H / h⌋, b = L / n, α = atan(H / L)
n — number of steps, H — floor height, h — riser, L — staircase length, b — tread, α — slope angle.
About the Stairs Calculator
The stairs calculator helps you design a straight single-flight staircase: from floor height and staircase length it computes the number of steps, actual riser height, tread depth, and slope angle, and draws a side-view diagram instantly.
The calculation targets comfort and safety: the comfortable-step rule is 2h + b = 600–650 mm, and the recommended slope for a residential staircase falls between 30° and 40°.
All computation runs in your browser: nothing is sent to a server, and the diagram redraws live as you change the inputs.
Benefits
Side-view drawing
Inline SVG diagram updates live and shows step proportions plus slope angle.
Code-based ranges
Hints for riser, tread, and slope ranges according to residential building codes.
Runs in your browser
No registration, no uploads — calculation and drawing happen on your device.
FAQ
What is the optimal staircase slope according to building codes?
For a main residential staircase the optimum is 30–40°. Up to 45° is acceptable for secondary flights; steeper angles are only used for attic or ladder-type stairs.
What is the comfortable-step rule 2h + b = 600–650 mm?
Twice the riser height plus the tread depth should add up to 600–650 mm. This matches the average human stride and keeps the climb effortless.
What tread depth is comfortable?
A comfortable tread is 28–30 cm — the full foot of an adult fits the step. Anything below 25 cm is acceptable only for secondary stairs.
What riser height works best?
Recommended riser height is 15–18 cm. Lower risers stretch the flight, higher ones make the climb tiring.
Do you need a riser board (kick plate) on stairs?
Closed risers stiffen the flight and make it safer, especially with kids around. Open risers look lighter but require slightly deeper treads and solid fastening.
How is the number of steps calculated?
It is the integer part of floor height divided by riser: n = ⌊H / h⌋. The actual riser is then recalculated as H / n so the flight lands exactly at the upper floor level.