Quick answer: For winder stairs, divide total rise by ~7.5 inches for the risers, subtract one for total treads, then split the turn angle (90° for L-shaped, 180° for U-shaped) evenly across your winder treads — 3 winders at 30° each is the most comfortable.
This winder stair calculator finds the risers, riser height, winder tread angle, and straight treads for an L-shaped or U-shaped staircase that turns with pie-shaped winder treads instead of a landing.
A winder staircase turns a corner using pie-shaped treads rather than a flat landing, so it fits a turn into less floor space. An L-shaped stair makes a single 90° turn; a U-shaped stair makes a 180° turn, often with winders at each corner.
A winder staircase turns a corner using pie-shaped (triangular) treads instead of a flat landing. It saves floor space compared to a landing and is common in L-shaped (90 degree) and U-shaped (180 degree) stairs.
Divide the total rise by about 7.5 inches for the number of risers, then subtract one for the total treads. Split the turn angle (90 or 180 degrees) evenly across the number of winder treads, and lay out the remaining straight treads at your normal tread depth.
The IRC requires winder treads to be at least 10 inches deep measured at the 12-inch walkline, and no less than 6 inches deep at the narrowest point. All winders in a flight must be consistent.
Most 90-degree winder turns use 2 or 3 pie-shaped treads. Three winders at 30 degrees each is the most comfortable, giving a gentler turn than two 45-degree winders.
Yes, when built to code. The main risk is the narrow inside corner, so keeping winders consistent, meeting the 10-inch walkline depth, and adding a continuous handrail on the outside of the turn make them safe.