How do I calculate BMI in children?

The way that BMI is calculated in children is different from the way it is calculated in adults. While the basic formula is the same; BMI = [weight / (height x height)] x 703, there are other considerations that are used in people under the age of 20.

In these cases, not only is this formula used, but also the age of the child as well as their gender is factored into the total calculation for body mass index. Read on to learn why a young person’s BMI is different from an adult’s and what to do if you think your child is overweight.

Use the BMI calculator on our home page and be sure to click on the child tab to calculate child BMI.

Why Your Child Gets Special Treatment

As an adult, there is no consideration taken into account regarding your age and your gender. For a child, however, both of these things are taken into consideration. Why? Well, the bottom line is that a child is still growing. An 8 year old girl may have a higher BMI than a 15 year old girl because the 8 year old still has her baby fat. These things are taken into consideration when a child’s BMI is determined.

When a child’s body mass index is being configured, their weight and height are compared to a national chart of children in their age group. They are ranked in a percentile of children, much like what happens when you take your child to the doctor for their annual physical. The doctor will pull out a growth chart and show you how your child compares to other children in the same age group. This is virtually the same; a child’s weight, height and age are placed on a chart by gender, their placement on that chart will determine their BMI index. If a child is in the 95 percentile, then they are considered overweight according to BMI charts.

What You Need to Know about Getting A BMI for A Child

The BMI index isn’t just for telling you if your child is overweight; it determines if he or she is underweight too. There are many changes going on in a child’s body when they are between the ages of 8 and 16 and, as such, they often look like walking scarecrows with their clothing hanging off. If your child is determined to be underweight, consider your child’s lifestyle. Are they eating well, do they get plenty of exercise, do they have a high-energy rate and output? If you answered yes to these questions, then you probably don’t have a reason to be concerned, especially if they gain weight over time.

However, if you said no to any of these questions, you may want to consider the possibility of your child having an eating disorder. Don’t get overly concerned yet, have a doctor evaluate your child and see what he or she has to say about your child’s weight.

In addition, some doctors object to the idea of placing a young child in the category of being overweight or obese if they have not yet reached puberty. A child who is active and eats relatively healthily may still be chubby, or even fat, until they reach puberty and their body balances out. Some doctors will not do a BMI assessment on a child under the age of 13 unless the child appears to be morbidly obese and other health risks are apparent. Regardless, the Center for Disease Control (CDC) and the American Academy of Pediatrics both recommend that BMI assessments be done to all children beginning at age two, as it can be a predictor of future health problems.

It is important to note that BMI assessments cannot be used as a diagnostic tool. What this means is that you can’t check your child’s BMI and assume that they are healthy or unhealthy based on the results. Only a doctor can assess the overall health of a child so it is important to maintain regular physicals for your children no matter what their BMI is.

Lastly, a BMI only determines the possibility of obesity; in order to determine fat to muscle ratio, you need to use a formula that determines the percentage of body fat your child has; a BMI doesn’t do this. However, a BMI is an excellent way to determine if there might be a problem. The truth is, you can look at your child and determine for yourself if they are fat or muscular. Muscular kids don’t have fat rolls or a round tummy and face. Keep that in mind before you decide to dismiss the BMI results for your child because you think they are simply ‘solid.’ When your child’s health is at stake, you can’t be too careful.

Using a BMI Calculator

The fastest way for you to determine your child’s BMI is for you to use a BMI calculator. Beware, however, not every BMI calculator can provide you with an accurate reading for a child. Ours can, however, and the link is conveniently located on this page. Make sure you select the child tab at the top of the calculator as well as the correct gender for your child so that you can get accurate results.

Our BMI calculator is easy to use, it takes seconds to input the information needed to calculate your child’s BMI, it is completely accurate and based on the CDC’s determination of what is normal, obese and underweight in the US. Lastly, the calculator is free, you won’t have to reveal your personal information and everything is completely anonymous.

Why not try it now?