Calculate dimensions for 90° or 180° winder stair layouts.
90° Turn (L-Shape)
180° Turn (U-Shape)
Calculation Results
Total Number of Risers:–
Actual Riser Height:–
Number of Straight Treads:–
Winder Angle (Average):–
Narrow End Tread Width (Estimate):–
Wide End Tread Width (Estimate):–
Total Going (Straight Flight):–
Understanding Winder Staircase Design
A winder staircase is a specialized design where the stairs change direction without the need for a flat landing. Instead, the steps themselves are tapered (pie-shaped). This is an excellent space-saving solution for homes where a full landing would consume too much floor area.
Key Components of Winder Stairs
Total Rise: The vertical distance from the finished surface of the lower floor to the finished surface of the upper floor.
Winder Treads: Tapered steps that are narrower on one side (the "inner" stringer) and wider on the other (the "outer" stringer).
Walking Line: An imaginary line, usually 300mm to 450mm from the inner handrail, where the tread depth should match the straight treads for consistent rhythm.
The "Rule of 3": Most standard 90-degree turns utilize 3 winder steps to maintain safety and ease of use.
Safety Standards and Codes
When designing winder stairs, safety is paramount. Building regulations typically require that:
The minimum width of the tread at the narrowest point (the "nosing" at the center of the turn) must meet local codes, often at least 50mm to 150mm depending on jurisdiction.
The riser height must remain constant throughout the entire flight, including the winder section.
The tread depth at the walking line must be consistent with the straight steps in the flight.
Example Calculation
Suppose you have a Total Rise of 2700mm and you want a Riser Height of 180mm.
Step 1: 2700 / 180 = 15 Risers.
Step 2: With 15 Risers, you have 14 Treads total.
Step 3: If you use a 90° turn with 3 winders, you have 11 straight treads remaining.
Step 4: If each straight tread is 250mm, your straight run is 11 x 250mm.
function calculateWinderStairs() {
var totalRise = parseFloat(document.getElementById('totalRise').value);
var stairWidth = parseFloat(document.getElementById('stairWidth').value);
var idealRiser = parseFloat(document.getElementById('idealRiser').value);
var turnType = parseFloat(document.getElementById('turnType').value);
var winderSteps = parseFloat(document.getElementById('winderSteps').value);
var treadDepth = parseFloat(document.getElementById('treadDepth').value);
if (isNaN(totalRise) || isNaN(idealRiser) || isNaN(stairWidth) || totalRise <= 0 || idealRiser <= 0) {
alert("Please enter valid positive numbers for Rise and Riser height.");
return;
}
// Calculation Logic
var numRisers = Math.round(totalRise / idealRiser);
var actualRiserHeight = (totalRise / numRisers).toFixed(2);
var totalTreads = numRisers – 1;
var straightTreads = totalTreads – winderSteps;
// Angle per winder
var anglePerWinder = (turnType / winderSteps).toFixed(1);
// Geometry for winders (Simplified Trigonometry for estimation)
// At the narrow point (assuming 50mm radius for the post)
var narrowEnd = ( (2 * Math.PI * 50) * (anglePerWinder / 360) ).toFixed(1);
// At the wide point (Outer stringer)
var wideEnd = ( (2 * Math.PI * (50 + stairWidth)) * (anglePerWinder / 360) ).toFixed(1);
var totalGoing = (straightTreads * treadDepth).toFixed(2);
// Display results
document.getElementById('resTotalRisers').innerText = numRisers;
document.getElementById('resActualRiser').innerText = actualRiserHeight + " mm";
document.getElementById('resStraightTreads').innerText = (straightTreads < 0 ? 0 : straightTreads);
document.getElementById('resWinderAngle').innerText = anglePerWinder + "°";
document.getElementById('resNarrowEnd').innerText = narrowEnd + " mm";
document.getElementById('resWideEnd').innerText = wideEnd + " mm";
document.getElementById('resTotalGoing').innerText = (totalGoing < 0 ? 0 : totalGoing) + " mm";
document.getElementById('stairResults').style.display = 'block';
}