BMI calculator
Body mass index compares weight against height. It is a rough screening measure for adults rather than a measure of health, and it says nothing about body composition.
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Enter height and weight in whichever units suit.
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What BMI is, and is not
Body mass index is weight in kilograms divided by height in metres squared. It was devised as a population statistic, not as an individual diagnosis, and it remains a screening tool rather than a verdict. It cannot distinguish muscle from fat, which is why a fit rugby forward and a sedentary person of the same weight and height read identically.
The standard adult categories
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25 to 29.9 | Overweight |
| 30 and above | Obese |
Where it does not apply
These ranges are for adults. They are not used for children, who are assessed against growth charts, nor during pregnancy. The thresholds are also lower for people of South Asian, Chinese, Black African and Caribbean background, where the health risks associated with a given BMI begin earlier. Anyone worried about their weight is better served by a conversation with a GP than by a number on a website.