Body mass index (BMI) is a measure of healthy weight – the relationship between your height and your weight. Multiply your height by itself (in metres) to get your height squared. Then divide your weight (in kilograms) by your height squared. The result is your BMI. A healthy BMI is between 18 and 25.
For example, a height of 1.75 metres multiplied by itself (1.75) equals 3.0625. So a weight of 70 kilograms divided by 3.0625 equals a BMI of 22.8.