How can healthy body weight calculators be accurate?

I've tried using the healthy body weight calculators over the net but they dont seem like they could be all that accurate. they NEVER take into account the size of a girls chest. how can they be accurate without doing so? im 5'3' and small boned, but I also am a DD. shouldnt that come into play when determining my ideal weight?
im not concerned about being obese, im around 115 lbs, but I do want to know what weight would be IDEAL for me.

115 is ideal for a women of 5'3

your weight is perfect and your lucky you got boobs lol