For adults aged 20 and over, a healthy BMI is 18.5 to 24.9 whatever your age; the official adult categories don’t change as you get older. Children and teenagers are different: their BMI is compared with others of the same age and sex on percentile charts, because body fat naturally changes as they grow. In later life, many researchers suggest not aiming lower than about 23–25, because keeping muscle and avoiding unintended weight loss matters more than a lower number.
Healthy BMI by Age at a Glance
| Age group | How BMI is judged | Healthy range |
|---|---|---|
| 2–19 years | BMI-for-age percentile charts (CDC in the US, WHO growth references internationally) | 5th to below 85th percentile |
| 20–39 years | Adult categories | 18.5–24.9 |
| 40–64 years | Adult categories, plus waist size | 18.5–24.9 |
| 65+ years | Adult categories; doctors also look at muscle, strength and weight changes | 18.5–24.9 officially; some studies suggest about 23–29 carries the lowest risk in older age |
Children and Teens: BMI Percentiles
A child’s BMI is calculated the same way (weight ÷ height²), but the result is placed on a chart for their exact age and sex:
| Percentile | Category (CDC) |
|---|---|
| Below 5th | Underweight |
| 5th to below 85th | Healthy weight |
| 85th to below 95th | Overweight |
| 95th and above | Obesity |
A BMI of 20 might be healthy for a 15-year-old and high for an 8-year-old, which is why adult categories never apply to children. See WHO BMI categories for adults and children.
Why Older Adults Are Treated Differently
- Muscle loss: after about 50, people lose muscle gradually; BMI can stay the same while fat increases and strength falls.
- The “obesity paradox”: several large studies found that in older adults, a BMI in the overweight range wasn’t linked to higher death rates, and being underweight was riskier.
- Unintended weight loss in older age can signal illness, so a falling BMI deserves attention.
This doesn’t mean higher BMI is healthy in older age; it means the number should be read alongside strength, waist size and overall health.
Check Your BMI and Healthy Range
Enter your height and weight in the free BMI Calculator to see your BMI and the healthy weight range for your height. Add your age and sex for an estimated body fat percentage and daily calorie needs. For your ideal weight at each height, see the healthy weight for height chart.
BMI by Sex
The adult categories are the same for women and men, but women typically have more body fat at the same BMI. See BMI for women by age and BMI for men by age.
Tips for Staying in a Healthy Range as You Age
- Keep lifting: two strength sessions a week slow age-related muscle loss.
- Eat enough protein, spread across meals, especially after 60.
- Stay active daily: walking, gardening and taking the stairs all count.
- Watch your waist, not just the scale.
- Report unplanned weight loss to a doctor promptly.
Frequently Asked Questions
What should my BMI be for my age?
For any adult aged 20 or over, 18.5 to 24.9. Children and teens are assessed with age-specific percentile charts.
Does BMI go up with age?
Average BMI tends to rise through middle age, but the healthy range doesn’t change. Older adults should focus on keeping muscle as well as weight.
What is a healthy BMI for a 60-year-old?
Officially 18.5 to 24.9. Some research suggests slightly higher values aren’t harmful in older age, so discuss your target with a doctor.
Can I use the adult BMI chart for my child?
No. Children’s BMI must be compared with growth charts for their age and sex.
Is BMI calculated differently for older people?
No. The formula is the same (weight in kilograms divided by height in metres squared) at every adult age. What differs is how doctors interpret the result alongside muscle mass, strength and recent weight changes.