Enter the total height you need to climb and this works out how many steps you need, the actual riser height once it's split evenly, the tread run, the stringer length to cut, and whether it clears the two IRC rules that trip people up most: max riser height and min tread depth.
You can't have a fractional step, so the math works backward from a whole number of risers: given your total rise and a maximum riser height, the minimum number of risers is ceil(total rise ÷ max riser height). Splitting the total rise evenly across that many risers is what determines your actual riser height — it's very rarely a clean number like exactly 7", and that's normal.
Stringer length is the straight-line diagonal from the bottom of the first riser to the top of the last one — the same right-triangle math (√(rise² + run²)) as sizing a rafter, just for stairs instead of a roof. Add a bit extra when cutting your actual stringer board for the horizontal seat cuts at top and bottom.
A common comfort rule of thumb, separate from code minimums: riser height + tread depth should land around 17–18", or (2 × riser) + tread around 24–25". Stairs that are too far outside that range often feel awkward to walk even if they technically pass code.