Body Mass Index (BMI) Calculation:
Body Mass Index (BMI)
BMI is calculated the same way for adults and children, based on the following formula:
Weight (in pounds)/(height [in inches])2 x 703
For adults 20 and older, BMI is interpreted using standard weight status categories:
| BMI | Weight Status |
| Below 18.5 | Underweight |
| 18.5 - 24.9 | Normal/Healthy Weight |
| 25-29.9 | Overweight |
| 30 and above | Obese |
For adolescents and children, however, BMI is interpreted differently, even though it is calculated using the same formula. Teens’ and children’s BMI need to be age- and sex-specific, because the amount of body fat changes with age and the amount of body fat differs between boys and girls. The CDC’s BMI-for-age growth charts take into account these differences and visually show BMI as a percentile ranking.
For 2-year-olds through 19-year-olds, obesity is defined as at or above the 95th percentile of children of the same age and sex.
BMI Chart for Boys:
BMI Chart for Girls:
