Stair calculator with landing

The riser math for a stair with a landing is identical to a straight stair. You still divide total rise by a target riser height, round to the nearest whole number, and divide back to get the actual riser height. A 108 in total rise at a 7.25 in target gives 108 ÷ 7.25 = 14.9, rounded to 15 risers, so each riser is 108 ÷ 15 = 7.2 in.

Where the landing changes things is total run. Instead of one long run of treads, you get two shorter runs of treads with a landing's worth of run in between. The landing doesn't get its own riser; it just sits flush with whatever step height the flight below it reaches.

So if you split 15 risers into an 8-riser lower flight and a 7-riser upper flight, the lower flight has 7 treads (risers minus one), the upper flight has 6 treads, and the landing fills the gap where an 8th tread would otherwise go on a straight run.

There's no single formula for how to split risers between the two flights; it's driven by the room. Common approaches are to split as close to even as the geometry allows, or to make one flight shorter so the landing lands at a specific point, such as clearing a window or door swing.

Whatever split you pick, every riser in both flights should still be the same height. You calculate the riser height once, for the whole rise, and use that same number for both flights. Don't recalculate riser height separately per flight or you'll end up with two different step heights meeting at the landing, which is a serious trip hazard.

1. Divide total rise by target riser height and round to get total risers for the whole stair.
2. Recalculate riser height as total rise ÷ total risers so it's exact.
3. Decide how many risers go in the lower flight based on the room layout.
4. Subtract to get the upper flight's riser count.
5. Each flight's tread count is its riser count minus one; multiply by tread depth for that flight's run.
6. Add landing depth plus both flights' runs for total horizontal run.

Commonly cited residential reference values call for a landing depth at least as deep as the stair is wide, with 36 in often cited as a practical minimum for a standard 36 in wide stair. A narrower stair could have a smaller code minimum, but most builders don't build landings shallower than 36 in because it feels cramped underfoot.

Landing width (side to side) generally needs to match or exceed the width of the stair itself. If the flight is 36 in wide, the landing should be at least 36 in wide too, so nobody has to squeeze past a doorframe or wall stepping onto it.

Codes vary by jurisdiction, and landing depth requirements can differ for a landing at a door versus a mid-flight landing with no door. Always confirm the actual minimum with your local authority having jurisdiction before finalizing a design.

A landing isn't a continuous stringer run, it's two separate flights that each need their own stringers, cut and framed independently. The lower flight's stringer spans its own rise and run; the upper flight's stringer spans its own rise and run starting from the landing platform.

For an 8-riser lower flight at 7.2 in risers and 10.5 in treads, rise is 8 × 7.2 = 57.6 in, run is 7 treads × 10.5 = 73.5 in, and stringer length is √(57.6² + 73.5²) ≈ 93.4 in. The 7-riser upper flight has a rise of 7 × 7.2 = 50.4 in, a run of 6 × 10.5 = 63 in, and a stringer length of √(50.4² + 63²) ≈ 80.7 in.

The landing itself needs its own framing, usually a small platform supported on posts or ledger-hung from a wall, built to carry live load independent of either stringer.

• Recalculating riser height separately for each flight instead of once for the whole rise.
• Making the landing shallower than the stair width to save floor space.
• Forgetting the landing counts toward total run when checking whether the stair fits the available floor space.
• Building the landing framing as an afterthought instead of planning its support before cutting stringers.
• Mismatching tread depth between the two flights, which changes the walking rhythm mid-stair.

A landing is worth the extra floor space when a straight run would be too long for the room, when you need a resting point on a tall flight, or when local code caps the number of risers allowed in one continuous flight without a break.

If you actually need to turn the stair 90 or 180 degrees rather than just break up a straight run, look at the L-shaped stair calculator or the U-shaped stair calculator, which handle the turned-landing geometry specifically. If you don't have room for any landing at all, the winder stair calculator swaps the landing for pie-shaped winder treads.