Number of steps, actual riser height, total run and stringer length for a staircase.
The calculator first finds the number of risers by dividing total rise by your target riser and rounding to a whole number, since you can't have a fraction of a step. It then divides total rise by that whole number of risers, which gives an "actual" riser height close to — but usually not exactly — your target.
The stringer is the diagonal structural board the steps sit on. It's calculated as the hypotenuse of a right triangle (√(Total Rise² + Total Run²)), so it's always longer than either the vertical rise or the horizontal run alone.
These compare your numbers against typical residential guidelines: riser height ≤ 7.75 in, tread depth ≥ 10 in, and the "comfort rule" that 2× riser + tread should total 24–25 in for a natural stride. They're typical values, not a substitute for your local building code.