Stair Calculator
Compute stair rise, run, stringer length, and number of steps from total height
Results
Step-by-Step Calculation
Understanding Stair Calculations
Building a safe, comfortable staircase starts with the right math. The total rise is the vertical distance from one finished floor to the next. Dividing that distance into equal steps gives you the riser height, while the tread depth determines how deep each step is. Getting these dimensions right keeps the stairs comfortable to climb and compliant with building codes.
Key Formulas:
- Number of Steps: round(Total Rise / Target Riser)
- Actual Riser Height: Total Rise / Number of Steps
- Total Run: (Number of Steps - 1) x Tread Depth
- Stringer Length: sqrt(Total Rise² + Total Run²)
Common Building Code Guidelines:
- Maximum riser height: typically 7.75 in (19.7 cm)
- Minimum tread depth: typically 10 in (25.4 cm)
- Riser consistency: risers should not vary by more than 0.375 in (9.5 mm)
- Comfort rule: 2 x Riser + Tread should equal 24 to 25 in
Related Calculators
Note: This calculator provides estimates based on standard stair geometry. Always verify your dimensions against local building codes before construction. Actual stringer length may need to account for tread thickness, the bottom riser cut, and the top connection to the floor framing.