My GP (who is also looking after my HRT requirements) wants me at a BMI of 25, no less. In other words, if you aim for any number in the normal range, you are good to go. I am 5'11 and have a BMI of 25. My GP gets grumpy if I lose more. For me to get to say 22, I would have to go down to the weight I was at 16 which was very skinny.
Remember that as useful as BMI can be, it is just a generalised average thing and can't take into account build, muscle mass or how fit you are which is why athletes "fail" at it.
If you have a BMI in the normal range (and definitely under 30 - just keep the doctors happy with a lowish number), stop worrying about the weight so much as fitness, wellness and self-acceptance. Much more rewarding than weight to height ratio.