Spiral Staircase Calculator
Treads and rotation for a spiral stair.
Enter your values
Enter the floor to floor height in in.
Enter the riser height in in.
Enter the staircase diameter in in.
Enter the total rotation in degrees.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Treads and rotation for a spiral stair. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Floor to floor height, Riser height, Staircase diameter, Total rotation |
| Main output | Number of treads |
| Formula | steps = rise / riser height; rotation per step = total rotation / steps |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Floor to floor height(in)
- Enter the floor to floor height in in.
- Riser height(in)
- Enter the riser height in in.
- Staircase diameter(in)
- Enter the staircase diameter in in.
- Total rotation(degrees)
- Enter the total rotation in degrees.
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.
What do I need to enter into the Spiral Staircase Calculator?
Just 4 values: floor to floor height, riser height, staircase diameter, total rotation. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Spiral Staircase Calculator work out the answer?
Spiral stair tread count comes from total rise divided by riser height; rotation is spread evenly across the treads. It applies the formula steps = rise / riser height; rotation per step = total rotation / steps and shows the working so you can check each step by hand.
Is the Spiral Staircase Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.