Stair Stringer Calculator
Calculate step count, rise/run per step, stringer length, and building code compliance for custom stairs.
Stair Stringer Calculator
Step count, rise/run, stringer length, and code compliance
Stair Dimensions
Floor to floor height
Leave blank to auto-calculate
Stringer Details
Treads
Layout
Number of Steps
5
Rise per Step
7.20"
Run per Step
10.30"
Total Run
41.2"
Stair Angle
41.1°
Materials
Stringers (2×12)
4× 4.6ft
Treads
5× 11.30" deep
Risers
5× 7.20" tall
Stringer Board Feet
25.6BF
Code Check
✓ Rise: 7.20" (OK: 4-7.75")
✓ Run: 10.30" (OK: ≥10")
✓ Rise+Run: 17.5" (Ideal: 17-18")
Formulas Used
Rise per Step
Rise = Total Rise ÷ Number of Steps
Divide the total floor-to-floor height by the number of steps to get individual rise.
Stringer Length
L = √(Total Rise² + Total Run²)
The stringer is the hypotenuse of the triangle formed by total rise and total run.
Stair Building Guide
IRC Residential Stair Code Requirements
| Parameter | Requirement | |-----------|-------------| | Max Rise | 7-3/4" (196mm) | | Min Run | 10" (254mm) | | Min Width | 36" (914mm) | | Max Rise Variation | 3/8" between any two risers | | Headroom | 6'-8" minimum |