How BMI is calculated
BMI = weight in kilograms ÷ (height in metres)2. In imperial units the calculator first converts pounds, feet and inches to kilograms and metres, so both modes give the same answer for the same person.
WHO adult categories
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 - 24.9 | Healthy range |
| 25 - 29.9 | Overweight |
| 30 and above | Obesity range |
What BMI cannot tell you
BMI is a quick screening number, not a measure of health. It does not know how much of your weight is muscle, bone or fat, nor where fat is stored. Athletes can have a high BMI and be healthy; some people with a "normal" BMI still have health risks. It is also designed for adults - not for children, teens (who use growth charts), or during pregnancy. For personal advice, speak to a doctor or dietitian.
Frequently asked questions
Is BMI accurate?
It is a rough population-level tool. Use it as one data point, not a verdict.
Does it work for children?
No. Children and teens are assessed with age- and sex-specific growth charts.
Do different countries use different cut-offs?
Some Asian health bodies suggest lower cut-offs for risk. This calculator uses the WHO adult bands.