BMI stands for body mass index. It’s a height-to-weight ratio and is one indicator used to determine healthy weight. The equation is your weight in pounds divided by your height in inches squared. You then take this number and times it by 703. A healthy BMI is between 18.5 and 24.9. But BMI doesn’t work for everyone. For example body builders and others who are very muscular may not be good candidates. So speak with your doctor about his or her thoughts on your weight.