Age 15 can defy the averages when it comes to the maturation and growth of boys and girls. By this age, many teenagers are starting to see their height remain the same, although some teens can still experience a growth spurt at this age.
Their weight is also starting to level-off and may remain fairly constant as long as they are active and eat a healthy diet. Because a teenager's body is still developing, the average weight of a teen can fluctuate quite a bit from one year to the next.
Even though determining the average weight and height of a 15-year-old is not an exact science, doctors and health experts still need screening tools to help monitor the health of teens.
How Doctors Determine What's Normal
The Centers for Disease Control and Prevention publishes its Growth Charts for the United States. This guide includes graphs to measure height, weight and body mass for children through age 20.
Pediatricians will track growth changes on these charts to determine whether the child is growing at a healthy rate or failing to thrive. Growing at a lower-than-average rate can indicate nutritional deficiencies, biological abnormality or inherited traits.
The weight-for-age graph lists the average weight of a 15-year-old boy at 126 pounds. The chart shows that children weighing 172 pounds score in the 95th percentile, or weigh more than 95 percent of boys their age. On the bottom end, boys weighing only 90 pounds fall in the 3rd percentile.
For girls, the average weight is 114 pounds. Girls at 86 pounds fall to the low end of the measurement scale, in the 3rd percentile. The 95th percentile of girls at age 15 is 168 pounds, meaning that they weigh more than 95 percent of girls nationwide.
The stature-for-age percentiles track the normal height for boys and girls. The average boy's height is 67 inches, or 5 feet 7 inches tall. Boys at 72 1/2 inches tall, or 6 feet and a 1/2-inch, are taller than 97 percent of all other boys in America, while those at 61 inches fall into the 3rd percentile.
For girls, 64 inches, or 5 feet 4 inches tall, is considered a normal height. To fall within the 97th percentile, a 15-year-old girl needs to only be 69 inches tall. A 59-inch tall — or 4 feet 11 inches — girl is in the 3rd percentile for height.
Normal Body Mass Index
There's a good chance a teenager will continue to see their body weight fluctuate as they get older. That's why body mass index (BMI) may be a more accurate way of determining what is normal for a 15-year-old. BMI measures the proportion of height, which can help determine risks associated with certain obesity-related diseases.
BMI is used to find out if a teen is underweight, of a healthy weight, overweight, or obese. Girls and boys differ in their amount of body fat as they mature, that is why BMI for teens, also known as BMI-for-age, includes gender and age.
A BMI between the 5th and 85th percentiles is considered healthy for children and teens. A teenager at the 85th percentile is considered overweight. Once crossing the 95th percentile, the teen is labeled as obese.
Based on this scale, a healthy 15-year-old boy has a BMI between 16.5 and 23.3. A BMI of 23.4 is at the 85th percentile, while an index of 26.8 would place the child in the obese category. Girls have a wider range of healthy weights, spanning 16.2 to 23.5. At 23.6, girls are considered overweight, while those above 28.1 are obese.
Teenagers that want to compare their BMI range to the BMI table for ages 20 and up, can cross-reference the following categories:
- Underweight: >18.5
- Normal weight: 18.5 to 24.9
- Overweight: 25 to 29.9
- Obese: 30 or greater