What Is the Winder Calculator?
Calculate winder stair dimensions with our free online tool. Winder stairs use pie-shaped treads to make turns without intermediate landings, saving valuable floor space in tight stair openings. This calculator handles both 90-degree (L-shaped) and 180-degree (U-shaped) winder configurations.
How to Use This Calculator
- Enter the total rise and standard tread depth for the straight sections.
- Set the number of winder treads (typically 3 for a 90° turn).
- Review the calculated tread widths at the walking line and narrow edge.
- Verify that the narrow-edge width meets the 6-inch code minimum.
Why Accurate Winder Calculations Matter
Winder treads are measured differently than rectangular treads. The IRC requires a minimum tread depth of 10 inches at the 12-inch walking line and at least 6 inches at the narrow end. Failure to meet these dimensions is a common reason for failed building inspections.
Building Code References
Related Tools
Frequently Asked Questions
How many winder treads do I need for a 90° turn?+
Three winder treads (each at 30°) is the most common configuration for a 90° turn. Two treads at 45° each are also possible but create a steeper transition.
Are winder stairs allowed by building code?+
Yes, winder stairs are allowed in the IRC for residential construction if each tread is at least 10 inches deep at the 12-inch walking line and at least 6 inches at the narrowest point.