Hi Ewe! (I love your name
Your BMI is based on your height and weight. We have a handy dandy BMI calculator right here at 3FC: BMI Calculator
When you plug in your height and weight, you'll get a number. The chart under the calculator will tell you what category you're in ... normal, overweight, obese etc. Any BMI between 18 and 24 is considered normal.
Hope that helps!