Stair Calculator
Calculate stair dimensions including rise, run, number of steps, and stringer length for safe, code-compliant stairs.
About This Calculator
How to Use
- Measure total rise (floor to floor height)
- Measure available run (horizontal space)
- Enter desired stair width
- Click Calculate to get step dimensions
📐 Stair Terminology
Rise: Vertical height of each step (typically 7-7.75")
Run/Tread: Horizontal depth of each step (typically 10-11")
Stringer: Diagonal support board that holds steps
Nosing: Overhang of tread beyond riser (typically 0.75-1.25")
🧮 Stair Formulas
📊 Building Code Requirements (IRC)
| Dimension | Minimum | Maximum |
|---|---|---|
| Rise | 4" | 7.75" |
| Run | 10" | — |
| Width | 36" | — |
| Headroom | 80" | — |
💡 Design Tips
- Ideal rise: 7" to 7.5" is most comfortable
- Ideal run: 10" to 11" for residential stairs
- Keep all risers within 3/8" of each other (code)
- Add handrails on both sides for safety
- Consider 42" width for moving furniture
❓ FAQ
What angle should stairs be?
30° to 37° is ideal for residential stairs. Steeper stairs are harder to climb; shallower stairs take more space.
How many steps for 9-foot ceiling?
A 9' (108") floor-to-floor rise typically needs 14-15 steps with 7-7.75" rise each.
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? Frequently Asked Questions
How accurate is this
This calculator uses standard formulas and provides accurate results for typical use cases. For professional or critical applications, always verify results with certified professionals or official sources.
Is this calculator free to use?
Yes, this Stair Calculator • Architecture • Calculator is completely free to use with no registration required. You can use it as many times as needed without any limitations.
Can I use this on mobile devices?
Absolutely! This calculator is fully responsive and works perfectly on smartphones, tablets, and desktop computers.
How do I interpret the results?
The results are displayed clearly with appropriate units. Refer to the "About This Calculator" section for detailed information.