Quarter-turn stairs with a landing: solve the riser split between flights, landing size, and the combined floor footprint.
An L-shape stair turns 90 degrees at a landing. The risers split across two flights; the landing replaces a tread and must be at least as deep as the stair is wide. The combined footprint is the lower flight run plus landing in one direction, and the upper flight run plus stair width in the other.
An L-shaped (quarter-turn) stair makes a single 90-degree turn at a landing, typically partway up the flight. It tucks a staircase into a corner, breaks the climb into two shorter runs, and gives a natural place to pause — which is why it is a popular choice for both homes and the landings that long flights require anyway.
The calculator divides your total rise into uniform risers across the two flights and sizes the corner landing. Under the IRC that landing must be at least as deep as the stair is wide and no less than 36 inches in the direction of travel. Choosing where the turn falls lets you balance the two flight lengths to fit the room; the landing itself replaces one tread and consumes a square of floor roughly the stair width on each side.