You can either use BMI calculators, the hamwi method, or reference a point in your life when you were happy with your weight (if relevant).
For me, I am 5’2 and aiming for 110lb. This matches with a mid-range healthy BMI, and the Hamwi method (100lb for the first 5 feet of height, plus 5lb for every additional inch - for women).
As a 5’4 female, BMI tells me I should be max weight of 145. I have rarely dropped that low and at my healthiest weighed 155 and wore a size 6. In my eyes size 6 is not overweight by any means although the BMI record tells me it is! I’m at 178 now and my goal weight is 155 :)
I’m 5’6” now and 69 years old. My lowest adult weight was 138. I had a 22 inch waist. It was also totally unsustainable for me. I don’t think I was there long enough to take a picture. The weight I was able to sustain for awhile was 163. Now my goal is 170. I know this is over recommendations. I used to carry weight in my thighs which made me look like I weighed less than I did. Now that I’m older my legs and arms are skinny and my middle is big. It is uncomfortable. I realize this is due to a lack of estrogen since hysterectomy at 45. Now I am on an estrogen inhibitor which even targets the estrogen my fat makes. I have lost 30lbs and my belly does not appear to be moving. My arms and legs are getting skinnier though. I’ll just have to keep trying and see whether my body wants me to lose another 30lbs.