BMI FAQs.

According to the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC), a healthy/normal BMI range for adults is 18.5 to 24.9 kg/m². Readings below 18.5 indicate underweight, 25.0 to 29.9 indicate overweight, and 30.0 or higher indicate obesity.

The mathematical BMI calculation is identical for both men and women: weight / height². Additionally, the standard healthy weight category boundaries (18.5 – 24.9) apply to all adults regardless of gender. However, women naturally tend to have a higher percentage of total body fat than men at the same BMI value, which is why clinical assessments sometimes look at body fat composition alongside BMI.

Yes, muscle mass is denser than body fat. Because BMI only relies on total weight and height, highly muscular individuals, such as athletes, bodybuilders, or regular weight trainers, may calculate an "overweight" or "obese" BMI despite having extremely low body fat and a healthy, fit body composition. For these individuals, waist circumference, waist-to-hip ratio, or body fat calipers are much more accurate metrics.

For children and teens (ages 2 to 19), BMI is calculated using the same formula, but the interpretation is different. Instead of fixed ranges, child BMI is evaluated using age-and-gender growth percentiles from growth charts (e.g., CDC charts). This is because children's body fat levels change rapidly as they grow, and differ significantly between boys and girls. Our calculator is optimized for adults (aged 20+). For children, you should consult standard pediatric CDC growth charts.