BMI Explained for Everyday Users

Body mass index is a screening ratio of weight to height squared. It is widely used because it is simple, but it does not directly measure body fat or overall health.

Adult BMI categories commonly used in public health communication include underweight (under 18.5), normal (18.5–24.9), overweight (25–29.9), and obese (30+). These cutoffs follow World Health Organization guidance for adults.

Athletes, older adults, and some populations may fall outside typical ranges for their health status. Treat BMI as one signal, not a diagnosis, and talk with a clinician for personal advice.