Body Mass Index (BMI)
Body mass index (BMI) is calculated as weight in kg divided by height in metres squared (kg/m²). These percentiles reflect the US population, which has one of the highest obesity rates among major countries (over 40% of US adults are obese). The median BMI in most age groups already falls in the WHO 'Overweight' or 'Obese' range. Being at the 50th percentile here is not a health target, it means half the US population has a higher BMI. For health guidance, refer to the WHO categories: Underweight (<18.5), Normal weight (18.5 to 24.9), Overweight (25 to 29.9), Obese (≥30). These thresholds are lower for East Asian populations (overweight ≥23, obese ≥27.5). Read more on Wikipedia
Body Mass Index (BMI) Norms by Age and Sex (kg/m²)
| Age | Sex | Percentile | ||||
|---|---|---|---|---|---|---|
| 5th | 25th | 50th | 75th | 95th | ||
| 20-29 | Male | 18.9 | 23.3 | 27 | 31.1 | 39.6 |
| Female | 18.6 | 22.2 | 25.5 | 31.6 | 45.6 | |
| 30-39 | Male | 21.2 | 24.9 | 27.8 | 33 | 42.5 |
| Female | 19.7 | 24.2 | 28.6 | 35.2 | 47.4 | |
| 40-49 | Male | 22.2 | 25.7 | 28.9 | 33.5 | 45 |
| Female | 19.7 | 24.6 | 28.5 | 35.1 | 45.6 | |
| 50-59 | Male | 21.6 | 25.5 | 29 | 33.3 | 44.6 |
| Female | 20.8 | 24.9 | 30 | 36.5 | 45.9 | |
| 60-69 | Male | 21.2 | 25.2 | 28.3 | 32.1 | 39.9 |
| Female | 20 | 24.8 | 28.8 | 34.5 | 42.5 | |
| 70-79 | Male | 21.6 | 25.6 | 28.8 | 32.3 | 39.2 |
| Female | 20.7 | 24.7 | 28 | 33.4 | 42.2 | |
| 80+ | Male | 21.1 | 24.6 | 27.2 | 30.2 | 34.8 |
| Female | 19.2 | 23.6 | 26.9 | 31.3 | 36.3 | |
What to expect by age group
Among US adults in their 30s, the middle 50% measure a BMI of 24.9 to 33.0 for men and 24.2 to 35.2 for women. BMI rises gradually through midlife and the median for most US adult age groups already falls in the WHO 'Overweight' or 'Obese' range. These percentiles reflect the US population, where obesity rates are among the highest globally, so norms skew higher than in most other countries, being at the 50th percentile here does not indicate a healthy weight target. Scores below 24.9 (men) or 24.2 (women) are below average for the US population in this age group; scores above 33.0 (men) or 35.2 (women) are above average.
| Age | Males | Females |
|---|---|---|
| 20-29 | 23.3 to 31.1 | 22.2 to 31.6 |
| 30-39 | 24.9 to 33 | 24.2 to 35.2 |
| 40-49 | 25.7 to 33.5 | 24.6 to 35.1 |
| 50-59 | 25.5 to 33.3 | 24.9 to 36.5 |
| 60-69 | 25.2 to 32.1 | 24.8 to 34.5 |
| 70-79 | 25.6 to 32.3 | 24.7 to 33.4 |
| 80+ | 24.6 to 30.2 | 23.6 to 31.3 |
Detailed Breakdowns
Select an age group and sex below for detailed percentile charts, tables, and ratings.
Frequently Asked Questions
What is a normal BMI?
The WHO defines normal weight as a BMI of 18.5 to 24.9. However, a WHO expert consultation (Lancet, 2004) found that Asian populations face higher health risks at lower BMI values, recommending action points of 23 for overweight and 27.5 for obesity. BMI alone does not account for muscle mass, bone density, or fat distribution.
How is BMI calculated?
BMI is calculated as weight in kilograms divided by height in metres squared (kg/m²). For example, a person weighing 70 kg who is 1.75 m tall has a BMI of 22.9. You can calculate yours using the CDC BMI calculator or the NHS BMI calculator.
Why is BMI controversial?
BMI does not distinguish between fat and muscle mass, so muscular athletes are often classified as overweight. It also does not capture fat distribution, abdominal fat carries more health risk than fat stored elsewhere. Additionally, the standard WHO thresholds were developed primarily from European populations and may not apply equally across ethnic groups.
Why are the median BMI values so high?
This data is from the US, which has one of the highest obesity rates among major countries, over 40% of US adults are obese. The median US male BMI is 27 to 29 across all age groups (WHO 'Overweight'), and for women in their 50s the median is 30 (WHO 'Obese'). In contrast, NCD-RisC (Lancet, 2024) shows mean BMI in Japan is around 23, South Korea 24, and most European countries 25 to 27, well below the US average of 29. Being 'average' in the US means something very different from being 'average' globally.