What is the difference between a half-turn stair and a dog-leg stair?

They describe the same basic layout: two parallel flights with a 180-degree turn. Dog-leg usually means the flights sit directly against each other with no well opening between them, while half-turn sometimes implies a small well gap. The calculation is the same either way.

How deep should the landing be on a half-turn stair?

The landing depth must be at least as wide as the wider flight it connects, with 36 inches as the residential minimum in most codes. Deeper landings, around 42 to 48 inches, make the turn noticeably more comfortable and make moving furniture far easier.

Can I use winders instead of a landing for the 180-degree turn?

Yes, and it saves roughly the depth of one landing from the footprint. Winders must still meet tread-depth rules at the walkline and at the narrow end, and most builders use at least six winders for a full 180-degree turn. Landings remain the safer and more code-friendly choice.

How much floor space does a half-turn stair need?

Plan on the combined run of both flights plus the landing depth for length, and twice the flight width plus any well gap for width. A typical 36-inch-wide residential half-turn stair with a 7.5-inch riser and 10-inch tread needs roughly 9 to 11 feet of length, depending on total rise.

How do I split the total rise between the two flights?

Divide the total rise by your target riser height to get the total riser count, then split it as evenly as possible between flights. Equal flights put the landing at the midpoint, keep every riser identical, and give both climbs the same comfortable rhythm.

Do I need handrails on both sides of a half-turn stair?

At least one continuous handrail at 34 to 38 inches above the nosings is required, running the full length of the stair including the turn. Stairs wider than about 44 inches, or with an open well between flights, generally need rails on both sides, so verify with your local code.

What headroom do I need where the upper flight passes over the lower one?

A minimum of 6 feet 8 inches of clear vertical space, measured from the nosing line of the lower flight to the underside of the upper flight. This crossover point is the most common headroom failure on half-turn stairs, so check it in the calculator before framing.

Half-Turn Calculator

What Is the Half-Turn Calculator?

A half-turn stair, often called a dog-leg stair, connects two floors with two parallel flights and a 180-degree turn in the middle. You climb the first flight, turn completely around on a flat landing (or a set of winders), and climb the second flight back in the opposite direction. This layout is the workhorse of two-story residential construction because both flights stack within nearly the same floor footprint, and the mid-flight landing breaks a long climb into two shorter, safer runs. This calculator splits your total floor-to-floor rise between the two flights, sizes the landing to match your stair width, and checks the critical pinch points: headroom where the upper flight passes over the lower one, uniform riser heights across both flights, and enough total run for the stair to fit your available floor space. Use it when planning a new stair, checking an existing layout against code, or preparing dimensions for an inspector or stair builder.

How to Use This Calculator

Enter the total rise: the vertical distance from the finished lower floor to the finished upper floor, including all flooring material on both levels.
Choose your turn type: a flat landing (simpler, more comfortable, easier to move furniture around) or winders (saves space but has stricter tread-depth rules).
Set your target riser height and tread depth. The calculator divides the total rise into whole risers and recalculates the exact riser height so every step is identical.
Enter the stair width for both flights. The landing depth must be at least as wide as the wider flight, typically 36 inches minimum for residential stairs.
Review the split between the lower and upper flights. Aim for an equal number of risers per flight so the landing sits at the midpoint of the total rise.
Check the headroom reading where the upper flight crosses over the lower flight or the landing. Code requires at least 6 feet 8 inches of clear headroom.
Review the total footprint: combined run of both flights plus the landing depth, and the overall width including any well opening between the flights.

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