BMI calculator

What is my BMI?

Use our BMI healthy weight calculator to see if you’re within the healthy weight range (18.5kg/m2 – 24.9kg/m2).

Enter your height in:
Enter your weight in:

What is BMI?

Body mass index (BMI) is a way of measuring whether you are a healthy weight for your height. It is used to categorise someone as being underweight, a healthy weight, overweight, or obese.

The categories for BMI ranges are as follows:

  • Underweight - below 18.5
  • Normal or healthy weight - 18.5-24.9
  • Overweight - 25-29.9
  • Obese - 30 and above

BMI Chart

Download this BMI chart.

How to calculate BMI

BMI is calculated by dividing your weight in kilograms by your height in metres squared.

How does this tool link to cancer?

There is strong evidence to suggest that being overweight or obese is a cause of 12 types of cancer.

Maintaining a healthy weight is one of our Cancer Prevention Recommendations. In fact, after not smoking, maintaining a healthy weight is one of the most important things you can do to help reduce your risk of cancer.

Situations where BMI is less reliable?

In general, BMI is a useful measure for most adults. However, BMI results may be a less reliable indicator for some groups of people, including:

  • Athletes, and those with a lot of muscle
  • some ethnic groups
  • older people
  • pregnant women
  • those less than 1.5m/5ft tall
  • children and teenagers
  • if your BMI is below 18.5, this puts you in the underweight range. Being underweight isn’t good for your health. Please speak to your GP as they can offer help and advice

If you, or the individual you are measuring, belongs to one of these categories you should speak to a doctor or other health professional to get a more accurate measurement.

What to do if I’m worried about my BMI results?

If our BMI calculator finds that your BMI is outside of the healthy range, we recommend you talk to your doctor before making any really big changes to your diet or the amount of physical activity you do.

However, don’t let that stop you making small changes today. If the BMI calculator finds you are more than the ideal weight, losing just a few pounds is a great start, and can improve your health and help to lower your risk of cancer and other diseases. If your BMI indicates you are less than the ideal weight, gaining some weight could benefit your health.