Stair Calculator
Enter your values below and click Calculate for instant results.
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Calculate rise, run, number of steps, and stringer length for any staircase. Includes IRC code compliance check.
Enter your values below and click Calculate for instant results.
Rise is the vertical height of each step. Run (or tread depth) is the horizontal depth of each step where your foot lands. The stringer is the diagonal structural member that supports the steps. Total rise is the floor-to-floor height the stairs must cover.
The International Residential Code (IRC) specifies maximum riser height of 7-3/4 inches and minimum tread depth of 10 inches for most residential staircases. Comfortable stair design often follows the rule of thumb: two rises plus one run should equal 24 to 25 inches (2R + T = 24-25"). A 7.5-inch rise with a 10-inch run equals 25, which is comfortable and code-compliant.
Every step in a staircase must have exactly the same rise. Variable rise, even by a fraction of an inch, creates a tripping hazard because your body develops a rhythm as you climb and any unexpected change breaks that rhythm. When calculating, the actual rise per step is determined by dividing total rise by number of steps, which this calculator handles automatically.