BMI Calculator

It is accurate as a quick population-level screen and poor as an individual diagnosis. Because it uses only height and weight it cannot tell muscle from fat, so athletes are routinely classified as overweight while someone with low muscle mass may sit in the healthy band despite high body fat. It also does not account for where fat is carried, which matters more for health risk than the total. Waist circumference and waist-to-height ratio are better single measures of metabolic risk.

The WHO defines 18.5 to 24.9 as the healthy range for adults. Below 18.5 is underweight, 25 to 29.9 is overweight and 30 or above is obesity. Some health bodies use lower thresholds for people of South Asian, Chinese and Japanese descent — commonly 23 for overweight and 27.5 for obesity — because cardiometabolic risk rises at a lower BMI in these populations.

Not in this form. Children and teenagers are assessed on BMI-for-age percentile charts, because healthy body composition changes substantially with growth. A raw BMI number is not meaningful under 20 years old.