Stair Stringer Calculator

Calculate riser count, actual rise, total run, stringer length, and code compliance for a straight staircase.

feet
inches
Code max 7¾″ · typical 7–7½″
Nosing-to-nosing · code min 10″
Code: ¾″–1¼″ if present
Number of risers13
Actual rise7.5385″
Total run10′ 0″
Stringer length12′ 10.9322″
Cut angle39.2°
Board needed13′ 10.9322″+12″ for attachment
Rise ≤ 7¾″ (actual: 7.54″) Rise ≥ 4″ Tread run ≥ 10″ (actual: 10″) Nosing ¾″–1¼″ (actual: 1″)

IBC residential stair code (IRC R311.7)

Key requirements for residential stairs in the US:

  • Maximum riser height: 7¾″ (7.75″)
  • Minimum riser height: 4″
  • Minimum tread depth: 10″ (nosing-to-nosing)
  • Nosing projection: ¾″–1¼″ if tread depth < 11″
  • Riser consistency: no two risers shall differ by more than ⅜″
  • Minimum headroom: 6′–8″

Always verify with your local building authority — some jurisdictions have stricter rules.