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HealthInfo Canterbury

Is my child a healthy weight?

He aha te taumaha hauora o tāu tamaiti?

Children come in different shapes and sizes – big, tall, small and short. There is a wide range of healthy shapes and sizes.

Children who stay a healthy weight tend to be fitter, healthier, better able to learn, and more self-confident. They are also much less likely to have health problems later in life.

The body mass index (BMI) is a way to find out if your child is the right weight for his or her height.

Finding out my child's BMI

You can work out your child's BMI using an online BMI calculator. If your child is 2 to 18 you need to use a calculator for children, as BMI is measured differently for adults. You will need to know your child's weight in kilograms and their height in centimetres. The calculator will tell you if your child is underweight, a healthy weight or overweight for their height and age.

You can use the following online BMI calculator from the UK site NHS.

After giving the BMI result, the calculator provides practical information about why the result matters. But the information is UK based. Take a note of the BMI result, but instead of following the link to Why this result matters, read the local information below about the BMI result.

content provided by NHS Choices


BMI result

BMI calculators for children give the results as a percentile. This shows how your child's BMI compares to other children of the same sex and age. For example, a girl on the 80th percentile is heavier than 80 out of 100 other girls her age.

Underweight (on the 2nd percentile or below)

If your child is underweight, it might be because they have inherited this from you or their other parent. But it could mean they aren't eating enough or they have an underlying health issue. Make an appointment to see your doctor or practice nurse. Find out more in Underweight children.

Healthy weight (between the 2nd and 91st percentiles)

Keep up the good work. For tips on helping your child maintain a healthy weight see Healthy & active children.

Overweight (91st percentile or above)

If your child is overweight, they are more likely to develop health problems. These could include high blood pressure, type 2 diabetes, breathing problems and joint pain. They are also more likely to become an overweight adult.

See Healthy & active children for tips on how to encourage your child to eat well and be more active. If you are concerned about your child's weight, talk to your doctor or practice nurse. If your child is 12 or under with a BMI at the 98th percentile or higher, they may be referred to a healthy lifestyle programme.

If your child is overweight and still growing, they don't need to lose weight. Staying the same weight while they grow taller will mean they will become a healthier weight for their height over time.

Written by HealthInfo clinical advisers. Last reviewed February 2018.


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