How BMI is calculated
BMI is weight in kilograms divided by height in metres squared. Under 18.5 is classed underweight, 18.5–24.9 healthy, 25–29.9 overweight, and 30+ obese.
Limitations
BMI is a rough screening tool. It can't tell muscle from fat and doesn't reflect where fat is carried, so athletes and some ethnic groups can be misclassified. Talk to a healthcare professional about your health.
Frequently asked questions
Is BMI accurate for children?
No. Children and teens are assessed using age- and sex-specific growth percentiles, not these adult categories.
What is a healthy BMI?
For most adults the range is 18.5 to 24.9, though health depends on many other factors.
