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A stair calculator takes the one measurement you know — the total height from one floor to the next — and works out everything else: how many steps, the exact riser height, the total run it will eat into the room, the stringer length to cut, and the angle. Most online stair tools stop at the step count; this one gives you the stringer and a comfort check too.
Get the rise right and the rest follows. The calculator keeps every riser identical (the code and safety requirement) and flags whether your riser/tread combination falls in the comfortable range builders use.
Number of risers = total rise ÷ target riser, rounded to a whole number; the actual riser height is total rise ÷ that number. Treads = risers − 1, total run = treads × tread depth, and the stringer is the hypotenuse: √(rise² + run²). The 2×riser + tread figure is the classic comfort rule (aim 24–25 in).
A 36 in total rise with a 7 in target gives 5 risers at 7.2 in each, 4 treads, a 44 in total run, and a stringer about 56.9 in (4 ft 9 in) long at 39°.