The body mass index (BMI) is a measure that uses your height and weight to work out if your weight is healthy.

BMI ranges

For most adults, an ideal BMI is in the 18.5 to 24.9 range.

If your BMI is:

• below 18.5 – you're in the underweight range
• between 18.5 and 24.9 – you're in the healthy weight range
• between 25 and 29.9 – you're in the overweight range
• between 30 and 39.9 – you're in the obese range

Accuracy of BMI

BMI 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.

You should not use BMI as a measure if you're pregnant.