Stair Calculator
Calculate stair dimensions including number of risers, tread depth, total run, and stringer length from floor-to-floor height.
Number of Risers—
Actual Riser Height—
Number of Treads—
Total Run (horizontal)—
Stringer Length—
How to Calculate Stair Dimensions
Number of Risers = round(Total Rise ÷ Desired Riser Height)
Actual Riser Height = Total Rise ÷ Number of Risers
Number of Treads = Number of Risers − 1
Total Run = Number of Treads × Tread Depth
Stringer Length = √(Total Rise² + Total Run²)
Actual Riser Height = Total Rise ÷ Number of Risers
Number of Treads = Number of Risers − 1
Total Run = Number of Treads × Tread Depth
Stringer Length = √(Total Rise² + Total Run²)
The number of risers is rounded to keep each step uniform. Treads are always one fewer than risers because the top landing counts as the final step.
Example:
Total rise: 108" (9 ft floor-to-floor), Desired riser: 7.5", Tread: 10"
Risers = round(108 ÷ 7.5) = 14 risers
Actual riser = 108 ÷ 14 = 7.71"
Treads = 14 − 1 = 13 treads
Total run = 13 × 10 = 130" (10.83 ft)
Stringer = √(108² + 130²) = 168.97" (14.08 ft)
Total rise: 108" (9 ft floor-to-floor), Desired riser: 7.5", Tread: 10"
Risers = round(108 ÷ 7.5) = 14 risers
Actual riser = 108 ÷ 14 = 7.71"
Treads = 14 − 1 = 13 treads
Total run = 13 × 10 = 130" (10.83 ft)
Stringer = √(108² + 130²) = 168.97" (14.08 ft)
Building Code Guidelines
Riser height: Max 7.75" (residential). Tread depth: Min 10". Riser + Tread rule: Riser + Tread should equal 17"–18" for comfort.
FAQ
What is the ideal riser height?
7" to 7.75" is considered ideal for comfort and safety. Code maximum is 7.75" for residential stairs in most jurisdictions.
How do I account for the floor finish?
Measure total rise from finished floor to finished floor. If finishes aren't installed yet, add the thickness of the flooring material to your measurement.
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Last updated: 2026-08-08