Enter your Staircase Height, Outer Diameter, Inner Diameter, Turning Angle, Riser Height, and Tread Thickness into the Spiral Staircase Calculator to find your Number of Steps, along with the Step Angle, Tread Depth, and both Outer and Inner Radius — everything you need before the build begins.
Number of Steps
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Step Angle
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Tread Depth
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Outer Radius
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Inner Radius
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Total Run
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For a 19-step spiral staircase with a 360-degree turn, each step would have an angle of approximately 18.95 degrees (360° ÷ 19 steps). This provides comfortable spacing between steps for safe navigation.
Handrail length is calculated using the helical path formula. It depends on the radius, total height, and turning angle. The length equals the square root of (circumferential distance² + vertical rise²).
Most building codes limit riser height to 200-220mm (7.75-8.66 inches) for spiral staircases. Some codes allow up to 241mm (9.5 inches) for private residential use, but lower risers provide better safety and comfort.
Building codes typically require a minimum diameter of 1500mm (60 inches) for residential spiral staircases. Commercial applications may require larger diameters, often 1800mm (72 inches) or more.
Tread depth is measured at the walking line, typically 600mm from the center. A minimum of 200mm (7.87 inches) is recommended at this point for safety and comfort, though 250mm or more is preferred.
Yes, spiral staircases can turn more than 360 degrees. This is useful for tall spaces or when you want to minimize the vertical space per step. However, more turns require careful consideration of headroom clearance.
Common materials include steel (most versatile), wood (warm appearance), and concrete (permanent, custom shapes). Steel is often preferred for the structure with wood or other materials used for treads and railings.