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BMI by age
The formula is the same at every age. How the result is read changes.
BMI is calculated the same way for everyone. What changes with age is the scale you compare it against.
| Age | How BMI is read |
|---|---|
| Under 2 | BMI is not used. Doctors use weight-for-length on WHO growth charts. |
| 2 to 19 | BMI-for-age percentile for the child's sex (CDC). |
| 20 to 64 | Standard adult categories: 18.5 to 24.9 is healthy weight. |
| 65 and older | Standard categories are used, but doctors interpret them with more context. |
Adults: the same cutoffs at every age
From age 20, the CDC and WHO adult categories apply regardless of age or sex: below 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 or above obesity. See the full adult BMI chart.
Why older adults get extra context
People tend to lose height and muscle as they age. That can raise BMI slightly while hiding a loss of muscle. Some studies find that a BMI a little above 25 is not linked to higher risk in older adults, while unplanned weight loss and weak muscle strength are clear warning signs. The research is mixed, so ask a doctor rather than choosing a new target on your own.
Children and teens
Under 20, BMI is compared with others of the same age and sex. Read our guide to BMI for children and teens.
Common questions
What is a good BMI for a 60-year-old?
The standard adult range of 18.5 to 24.9 is the usual reference. Doctors also weigh muscle, strength, and recent weight changes, especially after 65.
At what age do you switch from percentiles to adult BMI?
At age 20. Children and teens from 2 to 19 use BMI-for-age percentiles. Adults 20 and older use fixed categories.
Does a healthy BMI change as you get older?
The official cutoffs do not change with age for adults. How much weight a result tells you about health can change, which is why doctors look at the whole picture.