Body Mass Index (BMI) is a numerical value based on an adult's height and weight, this is used as a screening tool to estimate if a person has a healthy body weight. It is calculated by dividing weight in kilograms by height in meters squared. While BMI is useful for general population health, it does not distinguish between muscle mass and fat. To calculate your BMI, you can use the NHS BMI calculator here: Calculate your body mass index (BMI) - NHS - NHS
For most adults, if your BMI is:
- below 18.5 – you're in the underweight range
- 18.5 to 24.9 – you're in the healthy weight range
- 25 to 29.9 – you're in the overweight range
- 30 to 39.9 – you're in the obese range
- 40 or above – you're in the severely obese range
If you have an Asian, Chinese, Middle Eastern, Black African or African-Caribbean family background you'll need to use a lower BMI score to measure overweight and obesity:
- 23 to 27.4 – you're in the overweight range
- 27.5 or above – you're in the obese range
BMI score has some limitations because it measures whether a person is carrying too little or too much weight but not enough or too much fat. For example, people who are very muscular, like professional sportspeople, can have a high BMI without much fat.
But for most people, BMI is a useful indication of whether they're a healthy weight.