Stair Rise and Run Calculator
Calculate stair riser height, tread depth, stringer length, and stair angle. Checks IRC building code compliance automatically.
Stair Rise & Run Calculator
IRC code-checkedinches
IRC: 4" – 7¾"
IRC min: 10"
IRC min: 36"
Results
✓ Rise OK✓ Run OK2R+T = 24.50" (ideal 24"–25")
# Risers
16
# Treads
15
Actual Rise
6.750"
Stair Angle
31.5°
Total Horizontal Run
165"
13' 9.00"
Stringer Length
16.434 ft
Stair Width
36"
3.00 ft
108" ÷ 16 risers = 6.750" each · 15 treads × 11" = 165" total run
IRC Stair Code Quick Reference
| Dimension | Min | Max | Notes |
|---|---|---|---|
| Riser Height | 4" | 7¾" | Max variance between any two risers: 3/8 inch |
| Tread Depth | 10" | — | Measured nosing to nosing; min 11 inch with nosing |
| Nosing | ¾" | 1¼" | Required if tread depth is under 11 inches |
| Stair Width | 36" | — | Clear of obstructions |
| Headroom | 80" | — | Measured vertically from tread nosing |
| Handrail Height | 34" | 38" | Measured from tread nosing |
How to Use
- 1Measure floor-to-floor height (total rise)
- 2Enter your target rise per step (7 in is common)
- 3Enter tread depth (11 in is comfortable)
- 4Review riser count, stringer length, and code badges
Comfort Rules
2R + T = 24"–25" (best ergonomics)
R + T = 17"–18" (alternate comfort rule)
R = riser height, T = tread depth