BMI Calculator – Check Your Body Mass Index Online (Free)

How this works

BMI is your weight in kilograms divided by your height in metres squared. For adults the WHO bands are: under 18.5 underweight, 18.5–24.9 healthy, 25–29.9 overweight, 30 and above obesity.

In the UK, NICE advises lower thresholds for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, because health risks rise at a lower BMI: 23 for overweight and 27.5 for obesity.

Good to know

• BMI does not measure body fat directly — very muscular people can score “overweight”.
• It is not used on its own for children, teenagers or during pregnancy (children use age-and-sex centiles).
• Pair it with your waist-to-height ratio for a better picture.