How this works
BMI = weight in kilograms ÷ (height in metres)².
NHS adult ranges: below 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, 30 or above obese.
NICE recommends lower thresholds (23 and 27.5) for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, because risks start at lower BMIs.
BMI for under-18s is assessed with age- and sex-specific centile charts, so this adult calculator isn’t suitable — use the NHS children’s calculator instead.
This tool gives general information, not medical advice. If you have a health condition, are pregnant, or are worried about your eating or weight, please speak to your GP or a registered dietitian.
Questions people ask
Is BMI accurate for athletes?
Not always. Muscular people can have a high BMI without excess fat. Waist measurement alongside BMI gives a fuller picture.
What’s a healthy weight for my height?
We show the weight range that corresponds to a BMI of 18.5 to 24.9 for your height.
Does BMI work during pregnancy?
No. BMI isn’t used to assess weight during pregnancy — your midwife will advise you.