Body mass index (BMI) is a measure of body fat based on height and weight that applies to adult men and women. It takes into account natural variations in body shape, giving a healthy weight range for a particular height.

As well as measuring your BMI, healthcare professionals may take other factors into account when assessing if you're a healthy weight. Muscle is much denser than fat, so very muscular people, such as heavyweight boxers, weight trainers and athletes, may be a healthy weight even though their BMI is classed as obese.