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BMI Calculator

Enter your height and weight to calculate your Body Mass Index. All calculations run locally in your browser — nothing is sent or stored.

Units

Body Mass Index (BMI) is a screening figure derived from your height and weight. It estimates how your weight compares to a healthy range for your height. The categories above were standardised by the World Health Organization in 1997.

Limitations

BMI does not measure body composition. A muscular athlete may register as overweight despite having low body fat. BMI is also less accurate for older adults whose muscle mass has declined, for pregnant or breastfeeding people, and for populations whose body composition differs from the European reference group the ranges were originally built on.

When to see a doctor

Treat BMI as a starting point, not a diagnosis. If your result sits outside the normal range, or if you have concerns about your weight, body composition, or related conditions like blood pressure, blood sugar, or cholesterol, speak to a qualified clinician for a proper assessment.

Frequently asked questions

How is BMI calculated?

BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). When you enter imperial units, the tool converts your feet, inches, and pounds to metric first, so the result is the same either way.

What do the BMI categories mean?

The tool uses the World Health Organization ranges: under 18.5 is underweight, 18.5–24.9 is normal, 25–29.9 is overweight, and 30 and above is obese (split into classes I, II, and III on the scale).

Why might BMI be misleading for me?

BMI does not measure body composition, so a muscular athlete can read as overweight despite low body fat, and it is less accurate for older adults, pregnant people, and some populations. Treat it as a screening figure, not a diagnosis.

Is my height and weight data private?

Yes. Everything is calculated locally in your browser — your measurements are never sent to a server or stored.

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