Behind the number
Why a range and not a number
Bodies with the same height differ in frame, muscle, and fat distribution, so any single 'ideal' figure is false precision. The honest version of this question is: which weights sit inside the general adult reference band for my height? That gives you a span, often 15 to 20 kilograms wide, and where a healthy weight for you falls within it depends on things a height field cannot know.
How the range is calculated
This calculator takes the adult BMI reference band, from 18.5 up to the overweight cut-off at 25, and applies it to your height: the lower bound is 18.5 × height in metres squared, the upper bound is 25 × height in metres squared. At 175 cm that gives roughly 57 to 77 kg. It is the same arithmetic as the BMI calculator, run in reverse.
About the other formulas you may have seen
Older formulas like Devine, Robinson, and Hamwi produce single 'ideal body weight' numbers. They were developed decades ago, mainly to standardise medication dosing rather than as targets for the general public, and they disagree with each other by several kilograms. We show the BMI-band range instead because it is transparent about being a range.
How to use the result
Treat the range as orientation, not obligation. Being slightly outside it is common and not automatically a problem. Chasing the bottom of the range helps nobody. If you want to change your weight, start with what you eat day to day. That is the part CaloriSpy can show through your purchases.