Stair Calculator with Landing
Calculate L-shaped (90°) and U-shaped (180°) stairs with intermediate landings. Get separate rise/run calculations for each flight plus landing platform dimensions — all IRC code-checked.
Flight 1 (Bottom to Landing)
Flight 2 (Landing to Top)
Landing Platform
L-Shaped Stair Layout
IRC Landing Requirements
- R311.7.6 — A landing must be provided at the top and bottom of each stairway
- R311.7.6 — Landing width shall be at least the width of the stairway served
- R311.7.6 — Landing depth must be minimum 36" measured in the direction of travel
- R311.7.5.1 — Max riser height variation between any two risers: 3/8"
How It Works
1. Enter total rise — the full floor-to-floor height in inches.
2. Choose stair type — L-shaped (90° turn) or U-shaped (180° switchback).
3. Set landing height — where the landing sits relative to the lower floor. Default is halfway, but you can adjust to split flights unevenly if your layout requires it.
4. Set landing dimensions — width and depth in inches. Both must be at least 36" per IRC code. Width should match or exceed the stair width.
The calculator runs calcStairs() independently for each flight, giving you separate riser counts, rise/step, total run, stringer length, and code checks. The SVG diagram shows both flights with the landing platform between them.
Frequently Asked Questions
When do stairs need a landing?
IRC code requires a landing at the top and bottom of every stairway. An intermediate landing is needed when stairs change direction (L-shaped or U-shaped) or when the vertical rise of a single flight exceeds 12 feet. Landings are also recommended every 12-16 risers for comfort and safety.
What are the minimum landing dimensions?
Per IRC R311.7.6, the landing width must be at least as wide as the stairway served (minimum 36"). The landing depth (measured in the direction of travel) must also be at least 36". For example, stairs that are 42" wide require a landing at least 42" × 36".
What is the difference between L-shaped and U-shaped stairs?
L-shaped stairs make a 90° turn at the landing — flight 1 goes in one direction, flight 2 turns 90° and continues up. U-shaped (switchback) stairs make a 180° turn — the two flights run parallel in opposite directions, connected by the landing. U-shaped stairs take up less floor length but more width.
Can the two flights have different rise-per-step values?
Yes, if the landing splits the total rise unevenly, each flight will have a different rise per step. However, IRC requires that within each individual flight, the maximum variation between risers is 3/8". The calculator computes each flight independently to ensure code compliance.