1. BMI calculator

The body mass index (BMI) is a useful tool that uses your height and weight to determine if your weight is healthy. To calculate your BMI divide your weight in kilograms by your height in meters squared. 

Calculate your BMI here


For most adults, an ideal BMI ranges between 18.5 and 24.9. For children aged 2 to 18, the BMI calculation takes into account age and gender as well as height and weight.

If your BMI is:

  • <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

  • >40 - you are in the morbidly obese range

Accuracy of BMI

BMI gives a healthy weight range for a particular height.

However, as well as measuring your BMI, healthcare professionals usually take additional factors into account when assessing if you're in a healthy weight range (i.e. body fat, skeletal muscle mass etc.).

Muscle is much denser than fat, so very muscular people, including heavyweight boxers, weight trainers and athletes, may be at a healthy weight even though their BMI is classed as overweight or obese.

Your ethnic group can also affect your risk of some health conditions. For example, adults of Asian origin may have a higher risk of health problems at BMI levels <25.

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

2. Waist size matters

Measuring your waist is a good way to check you're not carrying too much fat around your stomach, as this fact can raise your risk of heart disease, type 2 diabetes and stroke. You may have a healthy BMI and still have excess fat around your tummy, which means you're still at risk of developing these diseases.

To measure your waist:

  1. find the bottom of your ribs and the top of your hips

  2. wrap a tape measure around your waist midway between these points

  3. breathe out naturally before taking the measurement

Regardless of your BMI, you should try to lose weight if your waist is:

  • 94cm or more (for men)

  • 80cm or more (for women)

You are at very high risk and you should contact your doctor if your waist is:

  • 102cm or more (for men)

  • 88cm or more (for women)