Free Stair Stringer Calculator
Calculate stair dimensions including number of steps, riser height, and tread depth. Ensures code-compliant stairs.
Vertical distance from finished floor to finished floor
Code max is typically 7-3/4 inches
Code minimum is typically 10 inches
Number of Risers
14
Number of Risers vs Total Rise (Floor to Floor)
How to Calculate Stair Stringers
Formula
Number of Risers = round(Total Rise / Desired Riser Height)
Actual Riser = Total Rise / Number of Risers
Number of Treads = Number of Risers - 1
Total Run = Number of Treads × Tread Depth
Stringer Length = sqrt(Total Rise² + Total Run²)
Building code typically requires: Max riser height 7-3/4 inches, min tread depth 10 inches, and the riser + tread combination should fall between 17 and 18 inches.
Example Calculation
A staircase with 108 inches (9 feet) of total rise, 7.5" desired risers, 10" treads, 36" wide.
- 01Number of risers = round(108 / 7.5) = 14 risers
- 02Actual riser height = 108 / 14 = 7.714 inches
- 03Number of treads = 14 - 1 = 13 treads
- 04Total run = 13 × 10 = 130 inches (10.83 ft)
- 05Stringer length = sqrt(108² + 130²) = sqrt(28,564) = 169 inches (14.1 ft)
- 06Stringers needed = 3 (for 36" width)
Frequently Asked Questions
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