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Tools / BMI calculator

BMI calculator

Calculates BMI in metric units and gives the standard category. It also says plainly what BMI is not — a population screening figure, not a diagnosis, and a poor guide for athletes, children and the elderly.

Runs entirely in your browser

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About this tool

Body Mass Index is a simple ratio of weight to height that is widely used as a quick screening figure for whether someone is in an underweight, healthy, overweight or obese range. This calculator computes BMI from height and weight in metric units and reports the standard category the result falls into.

Just as importantly, it is honest about what BMI is not. It is a population-level screening tool, not a diagnosis, and it does not distinguish muscle from fat or account for frame and fat distribution. That makes it a poor guide for athletes, for children and adolescents (who use age- and sex-specific charts), and for the elderly. The tool states these caveats so the number is read in context.

The calculation runs in your browser, so your height and weight stay on your device. Treat the result as a starting point for a conversation with a healthcare professional, not a verdict on your health.

Frequently asked questions

What is BMI and how is it calculated?
Body Mass Index is your weight divided by the square of your height (in metric, kg ÷ m²). It places you in a standard category and is used as a quick screening measure.
Is BMI an accurate measure of health?
It is a population screening figure, not a diagnosis. It cannot tell muscle from fat or account for body composition, so it should be interpreted alongside other information and professional advice.
Why is BMI unreliable for athletes or children?
Muscular people can register as “overweight” despite low body fat, and children and adolescents are assessed with age- and sex-specific charts rather than the adult categories.
What are the standard BMI categories?
The tool reports the conventional ranges — underweight, healthy weight, overweight and obese — based on your calculated BMI, while noting these are screening bands rather than clinical diagnoses.
Is my data kept private?
Yes. The calculation runs in your browser, so your height and weight are not sent anywhere.

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