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.
Divide total rise by 7.5 inches and round up to get the number of risers, then divide the total rise by that number for the exact riser height. A flight has one fewer tread than risers, because the top landing serves as the last tread — missing that is the most common stair-framing error. Codes commonly cap risers at 7¾ in and require treads of at least 10 in; your local code governs.
| Total rise | Risers | Riser height | Treads | Total run at 10 in |
|---|---|---|---|---|
| 16 in | 3 | 5.33 in | 2 | 20 in |
| 24 in | 4 | 6 in | 3 | 30 in |
| 32 in | 5 | 6.4 in | 4 | 40 in |
| 48 in | 7 | 6.86 in | 6 | 60 in |
| 96 in | 13 | 7.38 in | 12 | 120 in |
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.
Every constant this calculator uses and where it comes from, so you can check it rather than take our word for it.
Local codes amend the model IRC and adopt different cycles — your building department governs. Manufacturers revise yields; where your product's data sheet disagrees with a default here, use the product's number. See our full methodology.