Measuring Weight in Children

You may have heard your doctor use some different numbers or terms when talking about your child’s weight. The most precise way to measure obesity in a child is by using BMI-for-age percentiles. You cannot measure children’s weight using solely BMI. You must calculate BMI and then plot it on the BMI-for-age percentile graph to find the child’s weight status.

Some doctors discuss weight by referring to weight-for-age percentiles. When using weight-for-age percentiles, the doctor is not specifically measuring overweight in a child, but simply is comparing a child’s weight to others of the same age.

Measuring Weight Status Using BMI-for-Age Percentiles
Obesity in children (referred to as “overweight” in the weight status category table) is determined by using BMI-for-age percentiles. BMI-for-age percentiles have emerged as the favored method to measure weight status in children. This method calculates your child’s weight category based on age and BMI, which is a calculation of weight and height. However, it should be kept in mind that this method, among other methods, should be used as a tool, and only a physician can best determine and diagnose weight status in your child.

To plot a child’s BMI-for-age percentile, you must first calculate his/her BMI. To locate a BMI chart with weights and heights appropriate for children, please click the below link. Once you calculate his/her BMI, find the age of the child on the bottom of the BMI-for-age percentile chart (click on below link for boy or girl) and look to the left or right to locate their BMI.

Plot the point on the graph using a pen or pencil. Once you have plotted the measurement, locate the corresponding shaded color on the bottom of the chart to determine your child’s BMI-for-age percentile. You are then able to find your child’s weight status by viewing the Weight Status Category table located to the right of the chart.

BMI Chart

Girls BMI-for-Age Percentile Chart

Boys BMI-for-Age Percentile Chart

Measuring Growth in Children
You may have heard your pediatrician refer to your child’s weight in terms of a percentile. To measure growth in your child based on their weight, doctors most commonly use weight-for-age percentiles. Weight-for-age percentiles are used to measure your child’s weight based strictly on age. It does not take into account the height of a child. This is not a method to determine obesity (or overweight) in children, but simply an indicator of growth as compared to children of the same age.

To plot your child’s weight-for-age percentile, find the age of your child on the bottom of the chart and look to the left to locate their body weight. Once you locate their weight and age, plot the point on the graph using a pen or pencil. Once you have plotted the measurement, locate the corresponding shaded color on the bottom of the chart to determine your child’s weight-for-age percentile.

Once you have found your child’s weight-for-age percentile, you can then determine what percentile (or percentile range) they fall into, as compared to children of the same age. For example, if your child is in the 95th percentile, this means that their weight is greater than 95 percent of children of the same age.

Boys Weight-for-Age Percentile Chart

Girls Weight-for-Age Percentile Chart

About Body Mass Index (BMI)
BMI is the most common method to measure adult obesity. However, BMI is now becoming a popular tool, which is combined with BMI-for-age percentiles, used to measure obesity in children. BMI is a number calculated by dividing a person’s weight in kilograms by his or her height in meters squared. If your child’s BMI is not listed on this chart, please click here to calculate their BMI.



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