As children grow, the amount of body fat changes with age so BMI for children needs to be interpreted in relation to a child’s age. There are also gender differences. Therefore, for children and youth, BMI is age and gender specific. This means that the age and gender of a child must be considered when interpreting their BMI.

Related: Causes of Child Obesity

Once the BMI value has been calculated, it is plotted on a BMI-for-age Percentile Chart. Separate charts are used for boys and girls.

When the BMI (vertical axis) is plotted against the age (horizontal axis), it intersects to show which percentile or percentile range that particular BMI value falls within. See an example of a plotted graph.

Different percentiles or percentile ranges indicate different weight categories.


The percentile or percentile range shows the relative position of the child’s BMI among children of the same age and gender.

Related: Raising Healthy Kids

For children, BMI is used to determine if they are severely overweight, overweight, of acceptable weight, underweight or severely underweight. It is not a diagnostic tool. So, if you find that your child is overweight or underweight, it is best for you to consult your doctor to find out if he/she has any health problems associated with his/her weight.

Learn more about healthy weight for children and teenagers by downloading these booklets:

(1) Healthy Weight Healthy Children - for children and teenagers of all weight status
(2) Getting the balance right - for underweight children and teenagers

Visit Parent Hub, for more useful tips and guides to give your child a healthy start.

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