Stair Calculator
Design stairs, calculate riser height, tread depth, stringer length, angle, and check building code compliance. 3 calculation modes with step-by-step solutions.
Calculate
Select a calculation type, enter your measurements, and click Calculate to see stair dimensions, stringer length, and code compliance with step-by-step solutions.
Result
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Code Compliance
Step-by-Step Solution
Complete User Guide
What is the Stair Calculator?
The Stair Calculator helps you design safe, code-compliant stairs. Enter the total rise (floor-to-floor height), and it calculates the number of risers, riser height, tread depth, total run, stringer length, and angle — all checked against building codes (IRC/IBC).
3 Calculation Modes
Design
Total rise → risers, riser height, tread, run, stringer.
Riser & Tread
Given R, T, n → total rise, run, stringer.
Stringer
Rise + run → stringer length, angle.
Building Code Standards
| Parameter | Range | Ideal |
|---|---|---|
| Riser Height | 4–7.75" | 7" |
| Tread Depth | 10–14" | 11" |
| 2R + T Formula | 24–25" | 24.5" |
| Max Rise between landings | 12 ft | — |
Stair Terminology
📏 Riser — vertical face of the step
🦶 Tread — horizontal surface you step on
📐 Stringer — diagonal support beam under the steps
⬆️ Total Rise — floor-to-floor vertical height
➡️ Total Run — horizontal distance from top to bottom
Common Dimensions
🏠 Residential: 7" riser, 11" tread (2R+T = 25)
🏢 Commercial: 6.5" riser, 12" tread (2R+T = 25)
🪜 Steep: 7.5" riser, 10" tread (2R+T = 25)
🚶 Gentle: 6" riser, 13" tread (2R+T = 25)
Important Notes
- All risers must be uniform height (max ⅜" variation).
- Check local building codes — requirements vary by jurisdiction.
- Minimum headroom clearance: 6 ft 8 in (80 in).
- Handrails required on at least one side for 4+ risers.