Spiral Staircase Calculator
Treads and rotation for a spiral stair.
Enter your values
ⓘ Live results
Results
- Number of treads
- 12
- Actual riser height
- 9 in
- Rotation per tread
- 37.5°
- Walkline travel distance
- 19.63 ft
- Recommended min diameter
- 60 in for comfortable use
Quick answer
Spiral stair tread count comes from total rise divided by riser height; rotation is spread evenly across the treads.
steps = rise / riser height; rotation per step = total rotation / steps
How to use the Spiral Staircase Calculator
- 1Enter the floor-to-floor rise and a comfortable riser height.
- 2Enter the staircase diameter and total rotation desired.
- 3Check the walkline distance is long enough for a comfortable tread depth.
Worked example
Using the values the calculator loads with:
Inputs
- Floor to floor height108 in
- Riser height9 in
- Staircase diameter60 in
- Total rotation450 degrees
Results
- Number of treads12
- Actual riser height9 in
- Rotation per tread37.5°
- Walkline travel distance19.63 ft
- Recommended min diameter60 in for comfortable use
Frequently asked questions
Minimum spiral stair diameter?
Code minimums are often around 26 in for egress, but 60 in is far more comfortable for daily use.
How much rotation is typical?
Full spiral stairs commonly rotate 360-450 degrees between floors.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.