StairGen Pro › Concrete Stair Calculator with Landing
Guide & codes
This concrete stair calculator handles a straight reinforced concrete flight on a waist slab with a top landing, and gives you the concrete quantity and the rebar along with the steps. It suits stairs between floors, entrance steps and basement stairs, and helps you prepare the formwork and the material order.
From the stair height (Y), the flight length (X), the width (W), the top landing (L and E), the waist thickness (S), the nosing thickness (N) and the reinforcement (bar diameter and bars per step), the calculator returns the riser and tread, the concrete volume broken down by part, and the total length and weight of the bars. Switch on Folded plate to model a constant-thickness slab that follows the steps instead of a waist slab.
When to choose this stair
Choose a concrete stair when it has to last and never move: a reinforced slab with the steps cast on top, indoors or outdoors, and an upper landing to reach a door or a floor slab. It is the cast-in-place stair of entrances, porches, basements and shared areas.
Unlike the steel and timber stairs, there are no parts to cut, only volumes: the calculator gives the concrete for the steps, slab and landing, and the reinforcement (Ø6 mm, 4 bars per step). With “Folded plate”, the slab follows the profile of the steps at a constant thickness, uses less concrete and looks lighter from below.
Calculator parameters
Each dimension carries the letter used in the editor and on the drawings.
- YStair height
- default 1,600 mm · 300 to 6,000 mm
- Height climbed by the flight.
- XFlight length
- default 2,400 mm · 500 to 10,000 mm
- Plan length of the flight, excluding the landing.
- WStair width
- default 1,000 mm · 500 to 2,500 mm
- Clear width of the flight.
- LLanding length
- default 600 mm · 0 to 3,000 mm
- Depth of the top landing slab.
- ELanding thickness
- default 150 mm · 80 to 400 mm
- Thickness of the landing slab.
- SWaist thickness
- default 100 mm · 50 to 300 mm
- Thickness of the inclined slab under the steps (type 1).
- FNosing
- default 40 mm · 0 to 100 mm
- How far each tread overhangs the one below.
- NNosing thickness
- default 70 mm · 30 to 200 mm
- Thickness at the tread edge; on a folded plate, the plate thickness.
- ØRebar diameter
- default 6 mm · 6 to 25 mm
- Diameter of the bars.
- KBars per step
- default 4 · 2 to 12
- Bars spread across each step.
- CNumber of steps
- default 9 · 2 to 40
- Steps in the flight, including the top one.
How it's calculated
The height Y = 1,600 mm divided between 9 steps gives 177.8 mm per step. The length X = 2,400 mm over the same steps gives a run of 267 mm, and with the nosing F = 40 mm the tread depth is 307 mm. Step formula: 622 mm; pitch: 33.7°; verdict: “Comfortable stair”.
The concrete volume is worked out in parts: the landing (L × W × E), each step (the triangle formed by riser and run, times the width) and the waist slab of thickness S = 100 mm along the pitch line of the stair. With a folded plate there is no waist slab; a plate of thickness N follows the profile of the steps and uses less concrete.
The reinforcement is spread as 4 bars of Ø6 per step; the Data tab gives the number of bars, their total length and weight. This is a quantity take-off for estimating and ordering, not a structural design.
Result with the default values
Comfort verdict: Comfortable stair.
Complies with IRC / IBC
| Step formula 2R + G | 622 mm | 600 – 660 mm |
| Tread depth | 307 mm | ≥ 280 mm |
| Pitch | 33.7° | 30° – 40° |
| Riser | 178 mm | ≤ 197 mm |
| Going | 267 mm | ≥ 254 mm |
| Clear width | 1,000 mm | ≥ 914 mm |
| Guarding height | 900 mm | ≥ 864 mm |
Steps
| Riser height | 178 mm |
| Run (going) | 267 mm |
| Tread depth | 307 mm |
| Pitch | 33.7° |
| Waist slab length | 2,884 mm |
Concrete
| Landing volume | 0.090 m³ |
| Volume of one step | 0.026 m³ |
| Volume of all steps | 0.233 m³ |
| Waist slab volume | 0.288 m³ |
| Total concrete volume | 0.611 m³ |
Reinforcement
| Number of bars | 36 pcs |
| Total length | 36.00 m |
| Weight | 7.99 kg |
Building codes
The geometry is checked like any other stair, against the code picked in the Summary: under the IRC a riser of up to 7¾ in (196 mm) and a tread of at least 10 in (254 mm) for homes; under the IBC, risers of 4–7 in and treads of 11 in for other buildings; in England up to 220 mm of rise on a private stair. The structure is a different matter: waist thickness, reinforcement and cover must come from a design to the concrete code that applies (ACI 318 in the US, Eurocode 2 in the UK, AS 3600 in Australia, CSA A23.3 in Canada). The concrete class in the bill of materials, C25/30, is the European designation for roughly 25 MPa (about 3,600 psi) and is only a reference.
The calculator checks comfort (2R + G, going and pitch) and the building code of the country you pick in the panel (here, IRC / IBC for a dwelling): only the limits that code sets for riser, going, 2R + G, width, pitch, risers per flight and guarding. It is for guidance only: always confirm the code in force and local rules.
Building codes by country, with sourcesParts with the default values
The DXF (AutoCAD 2007, in millimetres or inches) carries these parts with their shop marks: one dimensioned sheet per part, the general arrangement and the bill of materials with weights.
What's in the DXF- B1HandrailTube Ø42.4 × 1
- B2BalusterRound bar Ø16 × 9
- H1Stair slabC25/30 × 1
- A1ReinforcementRebar Ø6 × 36
Frequently asked questions
How much concrete do I need for stairs?
Add up the landing, the steps and the waist slab. With the default values the total appears under “Result with the default values” and in the Data tab, broken down by part. It is a theoretical volume: add a margin for waste and spillage when ordering. To convert cubic metres to cubic yards, multiply by 1.308.
How do you calculate concrete steps?
First the steps, as on any stair: height divided by risers and length divided by treads, with 2R + G between 600 and 660 mm. Then the volume: landing, steps and waist slab. Finally the reinforcement. The calculator does all three at once and updates them as you type.
How thick should the waist slab of a concrete stair be?
It depends on the span and the load and must be set by a structural engineer. The default here is S = 100 mm, a common figure for short residential flights; change it and the volume is recalculated.
What is the difference between a waist slab and a folded plate stair?
On a waist slab stair (type 1) the steps sit on a slab of constant thickness parallel to the pitch line. On a folded plate stair (type 2), also called a sawtooth slab, a plate of constant thickness follows the profile of the steps, using less concrete and looking lighter from below.