Spiral Staircase Calculator
Construction & Home ImprovementCalculate the number of steps, tread angle, and arc lengths for a spiral staircase.
Number of Steps
Number of steps needed to keep each riser at or below the maximum.
Actual Riser Rise
7.200
Exact rise per step once the total rise is divided evenly.
Tread Angle
24.00
Angle of rotation each step covers.
Outer Arc Length per Tread
12.57
Arc length along the outer edge of each tread, the widest usable walking width.
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Odeh Ahwal0people find this calculator helpful
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Construction & Home Improvement calculators
Frequently Asked Questions
Why does the maximum riser rise matter here?
Rounding the number of steps up, rather than to the nearest whole number, guarantees no single riser ever exceeds the maximum you specify, which matters for both comfort and code compliance on a tightly wound spiral stair.
What is the tread angle?
It is how much the staircase rotates over the course of one step, found by dividing the total rotation by the number of steps. A tighter total rotation with fewer steps means a larger, more aggressive angle per tread.
Does this check headroom clearance?
No, this calculates the step count, rise, angle, and tread arc length only. Headroom, whether a person's head clears the step above as they climb, depends on the total rise, rotation, and diameter together and needs a separate check against your local code's minimum headroom requirement.
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