For years, doctors have used height and weight measurements to assess a child's physical growth in relation to other kids the same age. Now they have another tool: body mass index (BMI).
BMI is a calculation that uses height and weight to estimate how much body fat someone has. Doctors use it to determine how appropriate a child's weight is for a certain height and age.
You can use the BMI calculator below to determine your child's BMI, but it's also important to have your doctor perform regular BMI measurements. That way, you'll know the number is accurate and the doctor can discuss the results with you.
Starting when your child is 2 years old, the doctor will determine BMI at routine checkups and plot this measurement on a chart against those of other kids the same age.
Because what is normal changes with age, doctors must plot children's BMI measurements on standard growth charts rather than using a universal normal range for BMI as is done with adults. They also use separate charts for boys and girls to account for differences in growth rates and amounts of body fat as the two genders mature.
That information is recorded in your child's medical record, and over several visits the pattern of measurements allows the doctor to track your child's growth.
BMI is particularly helpful for identifying kids and adolescents who are at risk for becoming significantly overweight as they get older. In older kids and teens, there is a strong correlation between BMI and the amount of body fat. So those with high BMI readings — and, probably, high levels of fat — are most likely to have weight problems when they are older.
By identifying these at-risk kids, doctors can monitor their body fat carefully and try to prevent adult obesity through changes in eating and exercise habits.
BMI percentiles show how kids' measurements compare with others the same gender and age. For example, if a child has a BMI in the 60th percentile, 60% of the kids of the same gender and age who were measured had a lower BMI.
BMI is not perfect. For example, it's very common for kids to gain weight quickly — and see the BMI go up — during puberty. Your doctor can help you figure out whether this weight gain is a normal part of development or whether it's something to be concerned about.
Kids can also have a high BMI if they have a large frame or a lot of muscle, not excess fat. And a kid with a small frame may have a normal BMI but too much body fat.
Although BMI is not a direct or perfect measure of body fat, kids at or above the 95th percentile are considered obese, a term doctors use to indicate excess body fat, which increases the risk of weight-related health problems.
Kids who measure at the 85th to 94th percentiles are considered overweight, because of excess body fat or high lean body mass. A child whose BMI is between the 5th percentile to 85th percentile is in the healthy weight range. A child with a BMI below the 5th percentile is considered underweight.
Also, it's important to look at the BMI numbers as a trend instead of focusing on individual numbers. Any one measurement, taken out of context, can give you the wrong impression of your child's growth.
The real value of BMI measurements lies in viewing them as a pattern over time. That allows both doctor and parents to watch a child's growth and determine whether it's normal compared with that of other kids the same age.
While BMI is an important indicator of healthy growth and development, if you think your child may be gaining or losing weight too fast, talk to your doctor.
Reviewed by: Mary L. Gavin, MD
Date reviewed: September 2013
|Centers for Disease Control and Prevention (CDC) The CDC (the national public health institute of the United States) promotes health and quality of life by preventing and controlling disease, injury, and disability.|
|American Academy of Pediatrics (AAP) The AAP is committed to the health and well-being of infants, adolescents, and young adults. The website offers news articles and tips on health for families.|
|Growth Charts Doctors use growth charts to figure out whether kids' height and weight measurements are "normal" and whether they're developing on track. Here are some facts about growth charts.|
|Be a Fit Kid A lot of people talk about fit kids, but how do you become one? Here are five rules to live by, if you want to eat right, be active, and maintain a healthy weight.|
|What Being Overweight Means Being overweight has become a serious problem for many kids and adults. Find out what it means to be overweight in this article just for kids.|
|What's the Right Weight for My Height? One of the biggest questions guys and girls have is whether they're the right weight. Because the body is growing and changing so much during adolescence, it can be tough to answer this question.|
|What Is a BMI Report Card? Find out what the experts have to say.|
|I'm Not Fat. Why Does My BMI Say I'm Overweight? Find out what the experts have to say.|
|Overweight and Obesity It's an alarming statistic: 1 out of 3 U.S. kids are considered overweight or obese. Find out how to overcome overweight and obesity in your own family.|
|When Being Overweight Is a Health Problem A couple of pounds of extra body fat are not a health risk for most people. But when people are severely overweight, it can cause health problems.|
|Your Child's Growth From the moment parents greet their newborn, they watch the baby's progress eagerly. But how can they tell if their child is growing properly?|
|Body Mass Index (BMI) Body mass index (BMI) is a calculation that uses your height and weight to estimate how much body fat you have. BMI, although not a perfect method for judging someone's weight, is often a good way to check on how a kid is growing.|
|What Is a Growth Disorder? The other kids in the class have been getting taller and developing into young adults, but your child's growth seems to be lagging behind. Could a growth disorder be the cause?|
|Dealing With Feelings When You're Overweight If a person is struggling with extra weight, it can add to the emotional ups and downs of being a teen. Get some tips on coping here.|
|What's the Right Weight for Me? TV shows, movies, and magazines show pictures of people who are thin. Does that mean being thin is best? Not necessarily. Find out more by reading this article for kids.|
|Your Child's Weight "What's the right weight for my child?" is one of the most common questions parents have. It seems like a simple one, but it's not always easy to answer.|
|Body Mass Index (BMI) One of the biggest questions guys and girls have as they grow and develop is whether they're the right weight. One place to start is by learning about body mass index, or BMI.|
What to expect when coming to Akron Children's
For healthcare providers and nurses
Residency & Fellowships, Medical Students, Nursing and Allied Health
For prospective employees and career-seekers
Our online community that provides inspirational stories and helpful information.