BMI by Age: Adults, Seniors, and Children

BMI uses the same formula at every age, but the healthy interpretation shifts. Children use percentile charts; older adults may benefit from slightly higher BMI targets.

Children and teens (2–19)

Pediatric BMI is expressed as a percentile for age and sex, not fixed adult categories. A BMI at the 85th percentile indicates overweight; the 95th indicates obesity. Use CDC or WHO growth charts, not adult tables.

Young adults (18–40)

Standard WHO categories apply. This life stage is ideal for establishing baseline weight habits before metabolic changes of midlife.

Middle age (40–64)

Metabolic rate declines roughly 1–2% per decade. BMI may creep upward without dietary changes. Waist circumference becomes increasingly important as visceral fat accumulates.

Older adults (65+)

Research links BMI 23–29 with lower mortality in some senior cohorts compared to BMI below 23. Unintentional weight loss below BMI 22 in seniors warrants medical evaluation for sarcopenia or underlying illness.

When you are ready to calculate, use our free BMI Calculator — it runs privately in your browser and shows the formula used.

Frequently asked questions