Your body mass index (BMI) is a measure of your body fat. Their are much more precise methods for calculating your BMI. Using height and weight tends to overestimate body fat in athletes and others who have a muscular build and under estimate body fat in older persons and others who have lost muscle mass.
Generally, BMIs from 19 to 25 are considered healthy, BMIs from 25 to 30 are considered overweight, and BMIs 30 and above are considered obese.
Frame Size is used calculate your ideal body weight. Measure the circumference of your wrist at the smallest point, just below your wrist bone. If you don't have a flexible tape measure, just wrap a piece of string around your wrist and measure the string!