L-shaped stair calculator for iPhone.

An L-shaped or quarter-turn stair changes direction by 90°. Measure the finished floor-to-floor height and the space available in each direction. The two flight lengths include the turn area; they are not just the sum of the straight goings. Use the labelled plan to keep the endpoints consistent.

Height H

The vertical distance between the two finished floors.

Flight 1 length L1 and width W1

The lower flight’s overall plan length and its width. With a landing, the straight part has length L1 − W2.

Flight 2 length L2 and width W2

The upper flight’s overall plan length and its width. Its straight part has length L2 − W1. Widths can differ; do not replace them with one assumed common width.

Turn type and direction

Choose Landing or Winders, and Left or Right as you walk up the stair. Direction mirrors the plan; it is not your viewing direction from above.

Units

Use millimetres, centimetres or metres, or enter feet and inches. Results distinguish length, degrees and a count of risers.

Select Landing, a right turn and a top tread one rise below the upper floor. Enter H = 2800 mm, L1 = L2 = 2960 mm and W1 = W2 = 1000 mm. Calculate, then use the riser control to select 16 risers. This example uses metric units.

Each straight run is 2960 − 1000 = 1960 mm. Seven ordinary treads on each flight give 1960 ÷ 7 = 280 mm going. The landing is a separate level; the upper floor adds the final rise.

The main results give the total riser count, actual rise height, and going and pitch for each flight in landing mode. Unequal lengths or widths can produce different goings and angles, even though the rise height is shared.

Going is the horizontal advance. Pitch is the angle to the horizontal: in the example, atan(175 ÷ 280) ≈ 32.01°. Neither value specifies tread-board thickness, nosing projection or stringer stock.

The comfort card considers rise, going, pitch and 2 × rise + going. Its target band and messages are planning guidance from the app, not confirmation that your project complies with local requirements. The example’s 630 mm is an arithmetic check, not a safety certificate.

The numerical example above covers a landing. Switching to winders changes the geometry and can change the proposed riser count. The winder mode is explained here from its inputs and geometry; these landing numbers are not a worked winder layout.

Landing

A flat rectangular turning surface, kept separate from numbered ordinary treads. Its dimensions follow the two flight widths: W2 along the incoming direction and W1 along the outgoing direction. There is no separate landing-depth input on this screen.

Winders

The turn is divided into shaped treads. Pro² constructs their plan and walking line; a single rectangular going cannot describe every edge of a turning tread. The main going and pitch in this mode refer to the developed walking line.

Winder balance

The 0–100% Balance control changes how the turning layout spreads into the neighbouring flights. It is not a waste allowance or a percentage of completed work. Inspect the plan and individual tread contours after changing it.

The top connection has two choices. Level with floor puts the final numbered tread at the upper-floor level. One rise below keeps the upper floor as a separate final surface. This affects the number and distribution of ordinary treads.

For a landing, the count relation is: risers = ordinary treads + one landing + a final rise to the floor when the “one rise below” setting is selected. In the worked example that is 16 = 14 + 1 + 1.

The app first suggests a riser count. The − and + controls select another feasible count; the reset control returns to the recommendation when available. Recheck the connection setting when comparing alternatives.

The plan shows the turn direction and numbered surfaces. The elevation shows their heights and the upper-floor relationship. A landing is one level, even when the walking path across it changes direction.

The tread-detail cards use the actual surface contour: vertices, perimeter edges and interior angles. Straight, landing and winder shapes are distinguished, and matching shapes can be grouped. A winder’s inner and outer edges need not have the same length.

Use these drawings to understand the layout before making a cutting template. They do not add member thickness, joint details, cutting allowances or structural sizing.

• All dimensions must be positive and within the supported range. Each flight must leave usable straight length after the turn area is reserved.
• A combination can fail even when every individual dimension looks plausible. Change the available lengths, widths, turn type or riser count; a warning is not an instruction to force the layout to fit.
• The Balance control belongs to winders. It is hidden for a landing.
• This tool does not calculate cost, structural capacity, a compliant headroom envelope or regional building-code approval. Check those separately.

Is a quarter-turn stair different from an L-shaped stair?

On this page they describe the same overall 90° change of direction. Landing and winder variants use the same page, with different turning geometry.

Do I enter the length excluding the landing?

No. Use the overall flight lengths shown on the plan. In the landing example each 2960 mm length includes a 1000 mm turn allowance, leaving 1960 mm for ordinary treads.

Can I use the landing example for winder tread sizes?

No. A landing and a set of winders divide the turn differently. This fixed example uses a landing; inspect the recalculated plan after changing the turn type.