What is Body Mass Index (BMI) ?

No universal definition of "healthy weight" currently exists, as weight can be comprised of a different ratio of muscle, fat, and other factors. A highly muscular person may weigh very similarly to an obese person, but the two may not be equally healthy.

Nonetheless, for most of the population, weight is still a useful general indicator for health. The most common evaluation tool is the Body Mass Index (BMI) calculation, which takes height into consideration to determine a person's weight level.

According to the World Health Organization, a BMI < 18.5 is underweight, 18.5-24.9 is ideal, 25-29.9 is overweight, and >30 is obesity. As a rough idea, it is quite useful, though it cannot account for factors such as muscle and fat proportion or distribution. If your scale can measure body fat percentage, it may be a more useful indicator.

≦ 18.5
Normal (healthy weight)
18.5 ~ 24.9
25 ~ 29.9
≧ 30