What Is the Curved Calculator?
Design elegant curved and helical staircases with our free calculator. Curved stairs create a dramatic architectural focal point with a continuous arc radius, varying tread widths, and smooth railing transitions. This tool calculates arc length, tread geometry, and structural requirements.
How to Use This Calculator
- Set the inner and outer radii of the curved stair.
- Enter the total rise and number of treads.
- Review the calculated arc lengths, tread widths at the walking line, and headroom clearance.
Why Accurate Curved Calculations Matter
Curved stairs are custom-built and expensive, typically $10,000 to $100,000 or more, so accurate calculations before fabrication are essential. The walking-line tread depth must meet code minimums, and the continuous handrail requires precise radius matching.
Common Curved Mistakes to Avoid
- Confusing the inner radius with the outer radius when specifying the arc. Fabricators need both, since tread width and comfort vary significantly between the inside and outside edge of a curved run.
- Underestimating fabrication lead time. Custom curved stringers and matching handrail sections are typically shop-built, and errors caught after fabrication starts are costly to correct.