Help how do I know what my ideal weight is supposed to be?

Anonymous
I typed in my current weight in the bmi calculator. I am trying to lose weight for vanity and health reasons. Says I should be 150 at my height. Then while I was googling one of my favorite artists Katy Perry. I realized that she is the same height as me but she is 130 and she looks perfectly healthy. I don't want to be underweight. But if katy and I are the same height why does 130 on me look like I'm starving but 150 makes me look slim and healthy?
Help how do I know what my ideal weight is supposed to be?
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