Stair Building Basics
The IRC requires residential stairs to have a maximum riser height of 7-3/4" (7.75") and a minimum tread depth of 10". Risers within a staircase must all be within 3/8" of each other. Total rise divided by the number of risers gives riser height; the number of treads is always one less than the number of risers.
A good rule of thumb: Rise + Run should equal approximately 17-18 inches for a comfortable stair. For example, a 7" rise + 11" tread = 18" — comfortable and code-compliant. Always verify your local code requirements before building.
Note: IRC R311.7.1 requires a minimum 36-inch clear width for residential stairs and minimum 6'8" (80") headroom per R311.7.2. This calculator checks rise and run only — verify width and headroom separately.