What is the maximum riser height allowed by building code?

The International Residential Code (IRC R311.7) limits stair risers to a maximum of 7-3/4 inches (7.75 in) and requires a minimum tread depth of 10 inches. Consistent rise and run throughout a flight is also required.

How do you calculate stringer length for stairs?

Use the Pythagorean theorem: Stringer Length = √(Total Rise² + Total Run²). For example, a 9 ft (108 in) rise with a total run of 130 in: √(108² + 130²) = √(11664 + 16900) = √28564 ≈ 169 inches ≈ 14.1 ft.

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🛠️ Construction & DIY

Stair Stringer & Rise/Run Calculator

Calculate stair rise, run, number of steps, and stringer length based on total rise height and IRC code compliance.

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Total Rise (inches)

Floor-to-floor height in inches (9 ft = 108 in)

Target Run Per Step (inches)

IRC code min: 10 in; max rise: 7.75 in

Stair Design & IRC Building Code

Building codes (specifically the International Residential Code, IRC R311.7) define strict limits on stair rise and run to ensure safety. The maximum riser height is 7-3/4 inches (7.75"), and the minimum tread depth is 10 inches. Non-compliant stairs are more likely to cause trips and falls.

Stringer Length Calculation

Number of Steps = ⌈Total Rise ÷ 7.75⌉ (rounded up)

Rise Per Step = Total Rise ÷ Number of Steps

Total Run = Run Per Step × (Steps − 1)

Stringer Length = √(Total Rise² + Total Run²) [Pythagorean theorem]