The body mass index calculates body fat by an individuals weight and height.
A body mass index (BMI) less than 20 is considered low for most people. A low BMI could mean the individual is underweight and could be associated with health problems for some people.
A BMI of 20-25 is considered good. A could be a healthy weight for most people.
A BMI greater than 25 is considered high for most people. This could indicate overweight or obesity and may increase the risk of health problems.
However, the numbers do differ from person to person, and you should check your BMI with your personal physician.