# Demo of Spiral Stair Geometry Calculator

Given below the detailed description of an online construction calculator that is useful for computing spiral stair geometry.

The calculation can be made on the basis of the following factors :-.

Total Rise 8'- 4"

17 Rises of 5~7/8"

16 Runs (treads) at 6~9/32" inner ~ 13~19/32" outer

Outside Diameter 13'

Stair Angle Inner 43.1° ~ Outer 23.4°

160°

Inner Stringer Length 11'- 5~23/32" from top of first rise to upper floor

Outer Stringer Length 19'- 9~9/32" from top of first rise to upper floor

Tread Depth 12" from inner 8~13/32"

Angle at 12" from inner 35.1°

Handrail Radius Inner 5'- 7~9/16" Outer 7'- 8~9/16"

The following dimensions are needed for the calculation :-

The height of the stairs, Outside diameter, Inside diameter, Number of steps, The density of the steps, The rotation angle of the stairs

The length of steps in the spiral staircases should be upto or above 80 cm

Step width in the central part should not be under 20-25 cm at the widest part - nor surpassing 40 cm. The step height of Spiral staircase should be more than the height suggested for mid-flight of stairs. Normal step height for straight stairs is 16 cm whereas for spiral stairs the height is 18 cm.