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Spiral Stair Geometry - Metric

Total Rise Tread Depth at ? Stair tread codes state that each tread will have a minimum tread depth at specified measurement from narrow edge of tread. CHECK LOCAL CODES (See tread diagram) ? Ideal Rise is the rise you'd prefer. Actual Rise is calculated so that all rises to fit evenly into Total Rise, at nearest to Ideal Rise. Ideal Rise Actual Rise Inside Radius Widen Tread ? Widen and overlap tread for balusters etc - Widened treads must overlap to form correct geometry Tread Length Draw Chords Colour Rotation °

Rotation Inside Radius Scale

To print a paper template to mark outside tread curve, go to Full Scale Arc Templates and enter


Running Measurements explanation Not including Tread Widening
Inside Stringer = tread points winding up and around INSIDE of stairs from top of first rise to upper floor.
Outside Stringer = tread points winding up and around OUTSIDE of stairs from top of first rise to upper floor.
Inside Plumb = tread points vertically (plumb).
Inside Level = tread points around INSIDE LEVEL, (or flat, as marked AROUND a circle on the floor.)

Running Measurements:

Inside Stringer Mark-out

Outside Stringer Mark-out

Inside Plumb Mark-out

Inside Level Mark-out

Left click, release and drag to measure at scale inside diagram.

Spiral stair profile diagram with full dimensions

Spiral Staircase Handrail True Radius Calculator Enter actual rise of handrail for entered angle of rotation.

Flat Radius to Handrail Angle of Rotation Total Height for Rotation

Be sure to follow local building regulations regarding all stair dimensions.