StairGen Pro › L-Shaped Stair Calculator with Landing
Guide & codes
This L-shaped stair calculator with landing designs a quarter-turn stair: two wooden flights at 90° joined by a square landing (a quarter landing in UK terms). It is the way to gain height when there is not enough length for a straight flight, and the most common L-shaped staircase in houses.
Enter the total rise (Y), the run of the upper flight including the landing (X), the width (W) and how many steps go before (P) and after (Q) the turn. The calculator places the landing, checks comfort and produces the stringers, landing frame, newel post and railing with their sizes, plus a 3D model and DXF drawings. The step figures are the same for an L-shaped stair in steel or concrete, so it also works as a general stair calculator with landing.
When to choose this stair
The wooden L-shaped stair with a landing is the most comfortable and safest turning stair for a home: the landing splits the climb in two and there are no narrow treads at the turn. Choose it when the opening has two free sides and room for a 1,000 × 1,000 mm landing.
Compared with the 90° winder stair, the landing takes more floor area, but every tread keeps the same going from side to side and the landing is a good place to pause or turn a piece of furniture. With P = 6 and Q = 8, moving steps between the flights changes the landing height and the going of the upper flight, not the riser.
Calculator parameters
Each dimension carries the letter used in the editor and on the drawings.
- YTotal rise
- default 2,600 mm · 500 to 8,000 mm
- Height from the lower floor to the finished upper floor.
- XTotal run
- default 3,250 mm · 500 to 12,000 mm
- Plan length available for the flight (on turning stairs, the upper flight).
- WStair width
- default 1,000 mm · 500 to 2,500 mm
- Clear width of the flight.
- ZTread thickness
- default 50 mm · 3 to 120 mm
- Thickness of the tread (board or plate).
- FNosing
- default 50 mm · 0 to 100 mm
- How far each tread overhangs the one below.
- PSteps, lower flight
- default 6 · 1 to 25
- Steps before the turn.
- QSteps, upper flight
- default 8 · 2 to 25
- Steps after the turn, up to the top.
- TStringer thickness
- default 50 mm · 20 to 120 mm
- Thickness of the stringer board.
How it's calculated
The total rise Y = 2,600 mm is shared between 15 risers (6 steps below, the landing and 8 above), so each step rises 173.3 mm. On the upper flight, X = 3,250 mm minus the landing width (1,000 mm) leaves a run of 281 mm per step and a tread depth of 331 mm with the nosing.
With the default values the step formula gives 628 mm and the pitch 31.6°: “Comfortable stair”. A riser that is too high is fixed by adding steps to one of the flights; the Summary panel works out how many and applies them in one click. Watch the riser height in particular: for a US home it must not exceed 196 mm (7¾ in), and in England 220 mm.
To choose the split between P and Q, look at the opening: the lower flight usually starts against a wall and the upper flight arrives at the floor above. With Top tread one riser down, the last tread sits one riser below the upper floor and the floor itself becomes the final step.
Result with the default values
Comfort verdict: Comfortable stair.
Complies with IRC / IBC
| Step formula 2R + G | 628 mm | 600 – 660 mm |
| Tread depth | 331 mm | ≥ 280 mm |
| Pitch | 31.6° | 30° – 40° |
| Riser | 173 mm | ≤ 197 mm |
| Going | 281 mm | ≥ 254 mm |
| Clear width | 1,000 mm | ≥ 914 mm |
| Guarding height | 900 mm | ≥ 864 mm |
Steps
| Risers | 15 pcs |
| Riser height | 173 mm |
| Run (going) | 281 mm |
| Tread depth (run + nosing) | 331 mm |
| Open riser gap | 123 mm |
| Pitch | 31.6° |
| Nosing-to-nosing distance | 330 mm |
Wood
| Tread area | 4.174 m² |
Building codes
The landing must keep the full width of the stair. The IRC asks for a landing at least as wide as the flight it serves and limits a flight to 151 in (3835 mm) of rise between landings. Approved Document K asks for landings at least as wide and as long as the narrowest flight width. In Australia, the NCC allows 2 to 18 risers per flight. Headroom over the whole stair, including the landing, is 6 ft 8 in (2032 mm) under the IRC and 2.0 m in the UK and Australia.
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- Z1StringerBoard 50 × 2
- Z2StringerBoard 50 × 2
- E1Treadt=50 × 12
- E2Treadt=50 × 2
- M1Landing frameBeam 50×150 × 2
- M2Landing frameBeam 50×150 × 2
- R1Landingt=50 × 1
- P1PostTimber 100×100 × 1
- T1Risert=20 × 14
- B1HandrailRound timber Ø50 × 1
- B2BalusterBatten 35×35 × 14
- B3HandrailRound timber Ø50 × 1
Frequently asked questions
How do you calculate L-shaped stairs with a landing?
Count the landing as one more step: divide the total rise by all the risers, including the one onto the landing, and share each flight's run between its treads. Then check that 2R + G stays between 600 and 660 mm. The calculator does it all at once and lets you move steps from one flight to the other.
What are the dimensions of an L-shaped staircase with a landing?
The landing is a square as wide as the stair (1,000 mm with the default values). Each flight takes up its treads plus the landing, and the total footprint is shown in the Summary panel. If the opening is too small, the alternative is an L-shaped winder stair, which turns the corner with winder treads instead of a landing.
L-shaped stairs with a landing or with winders?
A landing is safer and more comfortable because the turn is made on the flat, and it gives you a place to rest and to turn furniture. Winders save space, but the treads in the turn are narrow on the inside.
Does it work for a steel or concrete L-shaped stair?
The step layout does: tread depth, riser height and the split between flights are the same. For a fabricated steel stair with brackets and a landing frame, use the L-shaped steel stair calculator.