BMI calculator
Work out body mass index, with the healthy weight range for your height.
- Runs in your browser — nothing you enter is uploaded
- No sign-up, no quotas, free to use as often as you like
How it works
BMI is the number forms, insurers and health services keep asking for. It is easy to calculate and widely misunderstood, so this shows the figure, the band it falls in, and the weight range that would put you in the healthy band for your height — which is usually the more useful answer.
How it is calculated
Weight in kilograms divided by height in metres squared. Imperial figures are converted using the exact international factors before the calculation, so the result matches the metric one precisely rather than drifting by a rounding error.
The standard categories
Under 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight, and 30 or above is obese. These are the World Health Organization bands used by most health services for adults.
What BMI does not know
It has no idea what you are made of. It cannot tell muscle from fat, which is why very muscular people often register as overweight or obese while being nothing of the kind. It does not account for build, age, sex or where weight is carried — and waist measurement is a better predictor of several risks. Treat it as one rough indicator, not a diagnosis.
It does not apply to children
Children and teenagers are assessed against age-and-sex percentile charts, not these fixed bands. A child's BMI number on this page is not meaningful.
BMI calculator — questions
Is BMI accurate?
It is a rough population measure. It cannot distinguish muscle from fat and ignores build and body composition, so a muscular person may register as overweight while being perfectly healthy.
Does it work for children?
No. Children are assessed on age-and-sex percentile charts rather than these fixed adult bands.
Can I use feet, inches and pounds?
Yes. Switch to imperial units; the conversion uses the exact international factors.
Is my height and weight sent anywhere?
No. The calculation runs in the page and nothing is stored.