Body mass index, or BMI, is a new term to most people. However, it is the measurement of choice for many physicians and researchers studying obesity. BMI uses a mathematical formula that takes into account both a person's height and weight. BMI equals a person's weight in kilograms divided by height in meters squared. (BMI=kg/m²). An imperial version is also available.

If you would like to calculate your BMI manually just follow these three steps.

1. Work out your height in metres and multiply the figure by itself.
2. Measure your weight in kilograms
3. Divide the weight by the height squared (ie. the answer to Q1.) For example you might be 1.6m (5 feet 3 inches) tall and weigh 65kg (10 stone). The calculation would then be:

1.6 x 1.6 = 2.56. BMI would be 65 divided by 2.56 = 25.39.