This BMI Calculator is designed to help you determine where your weight falls, given your gender and height, within the current World Health Organization recommendations for maintaining a healthy weight while following a heart-healthy lifestyle.
First, for adults aged 20 and older, the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) use a single, standardized set of categories that are independent of age or gender:
| BMI Category | BMI Range (kg/m2) |
| Underweight | Below 18.5 |
| Healthy Weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity | 30.0 or Greater |
Gender and Age in Adults: Although the classification ranges are the same for all adults, studies show that health risks associated with a given BMI can vary by gender and age. For instance, some research suggests a slightly higher optimal BMI for older adults. However, the official clinical guidelines maintain the single range for simplicity in population screening.
Child and Teen BMI Guidelines (Ages 2-19)
Unlike adults, BMI for children and teens is both age- and gender-specific. This is because children’s body fat composition changes dramatically as they grow and differs between boys and girls during development.
A child’s BMI is calculated and then compared to growth charts for their specific age and sex. The classifications are based on percentiles:
- Underweight: BMI below the 5th percentile.
- Healthy Weight: BMI from the 5th percentile up to the 85th percentile.
- Overweight: BMI from the 85th to the 95th percentile.
- Obesity: BMI at or above the 95th percentile.
The BMI Caveat
It is crucial to remember that BMI is a screening tool, not a diagnostic one. It does not measure body composition, meaning it can misclassify individuals with high muscle mass (like athletes) as “overweight” or “obese,” as muscle weighs more than fat.
Furthermore, it does not account for fat distribution, which is a key health risk indicator (e.g., abdominal fat is considered more dangerous). Due to differences in body composition and disease risk, some guidelines, particularly for Asian populations, recommend lower BMI cut-offs for defining overweight (starting at 23.0) and obesity (starting at 27.5).
A comprehensive health assessment should always consider BMI alongside other measures like waist circumference, blood pressure, and cholesterol levels.
—