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BMI Calculator

Weight against height, with the healthy range worked out for you.

What this calculates

Body mass index divides your weight by the square of your height. It is a screening tool, not a diagnosis — cheap to calculate, useful across a population, and blunt about any individual. It is worth knowing, and worth knowing the limits of.

Common questions

Is BMI accurate for me?

It is accurate at describing groups and rough at describing people. It cannot tell muscle from fat, so a lifter can read as obese while someone light with very little muscle reads as healthy. It also does not know where your fat sits, which matters more than the total.

What should I look at instead?

Waist circumference is a better single measure of the fat that carries risk — under half your height is the usual rule of thumb. A body-fat estimate adds more, and how your weight is trending over months adds more still.

Do the cut-offs apply to everyone?

No. The 25 and 30 thresholds were derived largely from white European populations. Several health bodies use lower cut-offs for people of South Asian, Chinese and some other ancestries, because the risk rises at a lower BMI.

Does BMI work for children?

Not this version. Children and teenagers are assessed against age-and-sex percentile charts rather than fixed numbers, because body composition changes so much through growth.

Estimates for healthy adults — not medical advice, diagnosis or treatment. If you are pregnant or breastfeeding, under 18, managing a condition such as diabetes or thyroid disease, or have a history of disordered eating, talk to a doctor or a registered dietitian before acting on any of this.

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Content last reviewed 29 August 2026. Estimates for healthy adults, not medical advice.