If you are a 54 inch girl how much should you weigh?

Hi there little girl...

What doctors tend to do is calculate your Body Mass Index (BMI). Which is an average calculation to determine whether you're

underweight

normal

overweight or

obese

Normal gives a BMI of 18.5- 24.9.
Your weight should be between 77 - 103.
Try not to cross 103 otherwise you'll be overweight.