Body Mass Index

A standardised ratio of weight to height, used as a general indicator of health.

The Body Mass Index (BMI) is a widely used health indicator. It can be roughly calculated by dividing your body weight (in kilograms) by your height (in metres) squared. If the resulting figure is less than 18.5, you are underweight. A number between 18.5 and 25 indicates a healthy weight.

A number above 25 is overweight and a number above 30 is obese. Although the BMI is a generally accepted health indicator, it is not the only one. For example, someone with a lot of muscle mass can have a high BMI without being unhealthy. By looking at the ratio of muscle to fat mass, among other things, you get a much better understanding of your health.