TopToolsAiCalculate your Body Mass Index (BMI) from your weight and height, and instantly see which BMI category — underweight, normal, overweight or obese — you fall into, along with the full reference range and a practical suggestion for your result. BMI is worked out as weight in kilograms divided by height in metres squared: someone who weighs 70kg and is 1.70m tall has a BMI of 70 divided by (1.70 x 1.70), or 24.2, which falls in the Normal range of 18.5 to 24.9, while someone weighing 90kg at 1.65m comes out at 33.1, in the Obese range of 30 and above. The formula was devised in the 1830s by the Belgian mathematician Adolphe Quetelet as a population-level statistical measure, which is why it remains the standard quick screening tool used by doctors and health organisations worldwide today.
Last updated: 1 Sep 2026
How to use BMI Calculator
- Enter your weight in kilograms.
- Enter your height in centimeters.
- Click "Calculate BMI" to see your BMI value and category (Underweight, Normal, Overweight or Obese).
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