Calculate your body mass index (BMI) for children and teenagers

Use this service to:

• check the BMI of children and teenagers aged between 2 and 17
• get information about what to do next

You should not use this tool to diagnose any symptoms. If you are worried about your or your child's weight, contact your local pharmacist or GP surgery.

Who should not use this tool

You should not use this tool if you, or the person you're using it for:

• are aged 18 or over
• are pregnant
• have been diagnosed with an eating disorder, or think you may have one
• have a condition that affects your height

How your BMI is calculated

A child or teenager's BMI is shown as a "centile". The centile result is shown as a percentage of how their BMI compares with other children or teenagers of the same age and sex.

For example, a girl on the 75th centile is heavier than 75 out of 100 other girls her age.

The BMI calculator works out if a child or teenager may be:

• underweight – on the 2nd centile or below
• a healthy weight – between the 2nd and 91st centiles
• overweight – 91st centile or above
• very overweight – 98th centile or above

The BMI calculation does not include muscle mass, which weighs more than fat.

Next steps

Overweight children are more likely to become overweight as adults. This could lead to long-term health conditions.

See a GP if you're concerned about your or your child's weight. They may be able to refer you to your local healthy lifestyle programme for children, young people and families.