Body mass index (BMI) is a simple ratio of your weight to your height: weight in kilograms divided by height in metres squared. It is popular because it is quick, free and easy to compare across large groups of people.
The standard BMI ranges
For adults, the commonly used ranges are: under 18.5 is underweight, 18.5 to 24.9 is the normal range, 25 to 29.9 is the overweight range, and 30 or above is the obesity range.
What BMI cannot tell you
BMI does not distinguish between muscle and fat, and it says nothing about where fat is stored. A muscular athlete can land in the overweight range while being very healthy, and someone with a normal BMI can still carry excess body fat. That is why it works best as a starting point, alongside measures such as waist-to-hip or waist-to-height ratio.
Try it yourself
Enter your height and weight below to see your BMI and how far you are from the edges of the healthy range.
BMI Calculator
Enter your values and calculate instantly.
This calculator is an educational estimate, not medical advice. Talk to a qualified professional before making health decisions.