What is BMI?

Body mass index is a measurement used to estimate your body fat. It is a measurement of weight in relation to height, and is the most widely accepted method used to screen kids and teens to determine weight status. It is a great tool to determine how you are growing, and how you compare with other kids and teens of the same age and sex. It is important to know your BMI because too much body fat can lead to unwanted illnesses and future health problems.

What is a BMI Percentile?

After BMI is calculated for kids and teens, the BMI number is plotted using the Centers for Disease Control’s growth BMI-for-age growth charts (for either girls or boys) to obtain a percentile ranking. The percentile indicates the relative position of the kid or teens BMI number among those of the same sex and age. The growth charts show the weight status categories used with kids and teens (underweight, healthy weight, at risk of overweight, and overweight).

BMI-for-age weight status categories and the corresponding percentiles are shown in the following table.

Weight Status Category Percentile Range
Underweight Less than the 5th percentile
Healthy weight 5th percentile to less than the 85th percentile
At risk of overweight 85th to less than the 95th percentile
Overweight Equal to or greater than the 95th percentile

Okay, I know what you are thinking, “What kid or teen really cares about their BMI? Not many, but what you do care about is how will you look in your new dress? Or will I score in tonight’s game? BMI does relate to the things you care about because it is a tool to help you focus on your health.

What does BMI do for you?

It moves you to action through awareness. Once you are aware, and have the knowledge about something it moves you to action. The action is determined by you. You may choose to do nothing (which is still action), or you may choose other actions. You have the power!

Calculating BMI

BMI is calculated and interpreted using the BMI Percentile Calculator. Before calculating BMI, one must obtain accurate height and weight measurements. This calculation can be determined by your physician, or as part of the “Get Fit” Team it can be calculated right here on our site.

Our calculator is for toddlers, kids, and teens. It calculates your BMI and allows you to see how you compare with other toddlers, kids, and teens in your same age group and gender. Remember once you have knowledge action follows.

BMI Changes


BMI for adults, kids, and teens are not the same. The BMI number is calculated the same way for kids, teens, and adults, but the criteria used to interpret the meaning of the BMI number for kids and teens is different from those used for adults. For kids and teens, BMI age-and-sex-specific percentiles are used for two reasons:

  • The amount of body fat changes with age.
  • The amount of body fat differs between girls and boys.

For adults BMI is interpreted through categories that do not take into account sex or age. There are separate charts for men and women. There are number ranges that are considered underweight, normal weight, overweight, or obese. No consideration is given for growth because adults have stopped growing and their age is no longer a major consideration. Kids and Teens are still growing and it is common for them to gain weight during certain times in growing up such as puberty.

What Happens When My BMI is High?

Don’t lose your mind! BMI is only one measure of your health. A more muscular kid or teen may have a higher weight and BMI, but not have more body fat. A smaller kid or teen may have a lower BMI, but more body fat. Whether big or small we all need to begin the journey of healthy living. Making better food choices and exercising daily can improve every child’s BMI. Diets are not the answer, but daily healthy habits will create healthy bodies for a lifetime.
Remember once you have knowledge action follows.

One Life, One Body, One Journey!