When Do Boys Stop Growing?

A group of young boys.

Even though they seem to get taller every year without fail, boys do, in fact, stop growing.

But unlike with girls who usually stop growing around age 14 or 15—or 2 to 2 ½ years after the first menstrual cycle—boys’ height-limiting age is more difficult to pinpoint. Nevertheless, the growth curve starts flattening from ages 18 to 20.

However, boys can stop growing anywhere from 17 to their early 20s in some cases.

To better understand the mechanisms at play behind their vertical development we’ll take a deeper dive into how they differ from girls, how puberty plays a part, and what to do if there are suspicions of a boy not reaching their potential height.

From Baby to Adolescent

The first few years of life are when some serious growing takes place. Children average 4 inches of growth from year to year, up until about the age of 4. From 4 years old onwards, the rate of growth decreases until they hit their pubertal growth spurt. This pre-puberty growth rate is usually in the ballpark of 2 to 2 ½ inches per year.

Then, puberty hits.

For girls, this happens from the age of 8 to 13, and for boys, it generally happens sometime between ages 9 and 14. While girls grow from 3 to 3 ½ inches per year during their growth spurt, boys can grow 4 inches per year. Children will usually reach their adult height from 4 to 5 years after their peak growth surge.

But while girls stop growing around the age of 14 and 15, boys can keep growing into their early 20s in same cases—but growth generally stops around the ages of 18 to 20. Another difference is that most girls hit their growth spurt significantly earlier than boys, about 2 years in fact. This means that many girls are taller than boys in early adolescence.

The timing of puberty, along with the genetics of the parents, both determine where a boy will fall on the growth curve. These genetic factors are intertwined with a number of environmental factors that all work to determine the height of a boy at any one age.

And while it might be more difficult to determine exactly when a boy stops growing, it’s safe to assume that the growth curve almost entirely flattens by the time boys reach the age of 20—with some exceptions growing into their very early 20s.

What is clear, however, is the close link between puberty and growth.

Height and Puberty

A conversation about height cannot be had without taking a look at puberty and the changes which occur during this time for boys. Nevertheless, it’s almost important to remember that each child has their own individual development timetable.

This is especially true when it comes to boys going through puberty since there’s such a wide variability because of their dramatic growth.

As most of us know, puberty for boys does not happen with a surge of hormones—specifically, testosterone. This flood of hormones is what spurs the changes in boys that usually happen between the age of 9 and 14.

Pubertal Changes for Boys

Along with height, there’s a number of changes that come along with puberty in boys.

One of these changes is the growth of pubic hair. Hair grows at the base of the penis and begins to darken. It spreads over the upper thighs and up to the navel throughout puberty. It’s also important to note that pubic hair begins growing before other body hair on the chest, underarms, and face.

The testicles and scrotum also begin to grow, almost doubling in size throughout puberty. The scrotal sac darkens and the testes hang lower, along with hairs appearing.

This change is paired with other body composition changes that come with a more thickset physique. Boys, unlike girls, tend to layer on muscle as their body goes through puberty, giving them a heavier look. Girls on the other hand tend to layer on fat to their body composition. Both sexes will have their bones become denser, all the way into their early 20s as well.

Voice changes also occur during this time. The voice may begin to crack as the voice box grows throughout puberty. This usually happens after the peak of the growth spurt. Along with voice changes comes the growth of the penis. The adult penis size can be developed anywhere from age 13 to age 18.

Furthermore, boys also tend to develop breast tissue during puberty. This is because the male hormone, testosterone, converts to estrogen inside of the body due to a chemical process. Estrogen is the female hormone, which can give boys going through puberty, breast buds. This is called gynecomastia—a condition that usually resolves itself within 1 or 2 years of developing. If this condition either occurs too early or sticks around late, then it’s recommended to consult a doctor.

The Tanner Stages

The Tanner stages are a way in which we can measure the development of an adolescent boy. It specifically looks at two things: pubic hair and genital development.

These stages consist of five different levels, all corresponding to different testicular volumes, penis sizes, and the amount (and type) of pubic hair. Stage one corresponds to no signs of puberty in the boy, while stage five means that the body has fully grown into its adult form.

Using the Tanner stages along with the growth chart, a doctor can see how far along a boy is in their development during puberty. Both of these things can be useful tools in determining whether a boy is on track, or whether extra tests and steps should be taken in order to make sure everything is going smoothly.

Height During Puberty

There tend to be the boys who mature early, starting around the ages of 11 or 12. Then there’s those who mature later, around the ages of 13 or 14.

Whether the boy falls into the former or the latter group doesn’t matter all that much, since both groups tend to gain the same average amount of inches in height. The one difference is that those who mature late tend to grow faster in order to make up for the time they’ve lost.

The average age-adjusted height that American men will reach from 20 years old onwards is 69.1 inches, or just over 5’9”.

On the other hand, at age 10 (which is one of the earliest starts for puberty), the median height for boys will be 54.5 inches.

The Center for Disease Control’s male growth chart is a fantastic way to gauge how tall a boy might grow, and for how much longer. But speaking of estimating heights, there are two ways to go about it.

Predicting Height

While there is no way to predict height that’s 100% accurate, there are two commonly used methods that can get results that are close enough to be useful.

The first method, which is the most popular, is the “mid-parental height calculator”. As the name suggests, it takes the heights of the parents of the boy to predict his potential height. While it exemplifies the importance that genetics play when it comes to height, it’s also very inaccurate. If you do use this method, be sure to keep within a ballpark range of minus 3 ½ or plus 3 ½ inches to your final height.

The way this method works is by adding 5 inches to the mother’s height and then adding that sum to the father’s height. When you divide that number by 2, it will give you the mid-parental height estimate.

So, for example, let’s take a father who’s 5’10” and a mother who’s 5’5”.

With the mother’s height of 5’5”, add 5 inches to 5’10”. Adding that to the father’s height of 5’10”, you get 11 feet and 8 inches. Dividing this number by two, you get your estimate: 5 feet and 10 inches. But as we mentioned above, keep in mind the significant margin of error. The true height could really be anywhere from 5’6” to 6’2”—especially keeping in mind the number of variables that come into play when deciding the height of a person.

This differs from predicting a girl’s height. If looking to predict the final adult height of a girl, you would subtract 5 inches rather than add 5. But in general, the taller the parents, the taller the child will be.

The Growth Chart

The other method which seeks to find an estimated height is the growth chart.

This method is as simple as checking out the CDC’s growth chart for boys between the ages of 2 and 20 and then following the line depending on what percentile the boy falls into. So, for a 10-year-old boy in the 50th percentile (half of all boys are shorter), he would stand at 61 inches tall.

Following the curve on the chart, one would expect that the boy reaches an adult height of 69 to 70 inches, or about 5’9” to 5’10”.

The chart can also be used for showing potential adult weight—this also depends on percentiles and curves but is more dependant on diet and activity levels.

What’s most important to note is that it doesn’t matter in which percentile the boy falls into, but it does matter that they stay in their percentile. What does this mean?

Consistency is important, and it’s important to take note that boys are following their curve. If a child drops from the 50th percentile to the 20th, there might be some underlying causes that need to be fixed right away. It’s also important to note that the growth curve is less exact at younger ages, and boys are more prone to jumping around percentiles when younger. However, an older adolescent should stick to their percentile consistently.

There’s a number of reasons why a boy might not be following their respective curve.

What Affects Height?

Genetics are the most important indicators of height—if the father and mother are tall, chances are the child will be tall as well. But that’s not the end of the story, there’s a number of reasons why a boy might be shorter (or taller) than expected.

One of the most important of these “nurture” aspects is the nutrients that adolescents consume. Children who are living in poverty and malnourished may not reach their full adult height growth during puberty. It goes without saying that the human body needs the proper macronutrients, the proper ratios of macronutrients (fats, carbs, and proteins), vitamins, and minerals, in order to properly develop and function.

The time when a child is developing, especially during puberty, is an essential time for proper nutrition to take place in order for the child to fully maximize their potential growth. Even if a boy does not show any deficits when it comes to body weight and height, it’s a good idea to check the growth chart to make sure that everything is on track.

But even if an adolescent may have been malnourished early on during puberty, it is possible for the body to bounce back in its growth when a proper, well-rounded diet is introduced again before adulthood.

Other Factors that Affect Height

There are some medications that can slow down growth. One of the most prominent examples is the overuse of corticosteroids. This medication an anti-inflammatory agent that aids in asthma and arthritis. However, if used excessively during puberty, it also has the potential of slowing down growth.

It should also be noted that those diseases that require corticosteroids can also negatively affect growth. Some studies have also shown that ADHD medications can possibly slow down growth, but the research doesn’t show a consensus with results so it’s also a better idea to consult with a doctor first.

Long term chronic diseases can also have a negative impact on potential growth. This includes diseases such as celiac disease, kidney disease, and cystic fibrosis—among others. All of these can result in shorter potential adult height. Cancer is also among these diseases, with children who have battled it ending up shorter in their adult lives.

Hormonal imbalances may also negatively affect growth in adolescent boys. For example, low thyroid or low growth hormone levels can have detrimental effects on height in puberty and going forward in adulthood.

Lastly, there are genetic conditions (other than those outlined by the mother and father) that play an important role in the potential height of a boy. For the most part, these are considered atypical conditions that play a negative role in height. This includes things such as Noonan syndrome, Turner syndrome, and Down syndrome—all leading to shorter children.

On the other hand, we have a condition known as Marfan syndrome. This syndrome affects the connective tissues within the body and can be life-threatening in extreme cases. But what makes it unique is that children with Marfan syndrome actually grow taller than expected, with longer fingers and arms.

Boys that have healthy diets typically tend to grow more than those who don’t, though genetics are the most important factor.

How Growth Problems Can Be Detected

As we mentioned above, the best way to see if a child is growing normally is to check their growth curve. If they’re staying consistently within their percentile, then everything should be fine—even if they’re relatively short.

It’s more of an issue if the child seems to be crossing percentiles. But even then, this is more common during the early years of puberty and is usually a sign of a constitutional growth delay—otherwise known as being a “late bloomer”.

However, it’s possible to detect potential problems by noticing any chronic problems that might be occurring, such as vomiting, fever, diarrhea, weight loss, poor nutrition or appetite, or a significantly delayed puberty. If these issues are noticed, it’s best to go to a pediatrician to make sure that the child is on track according to their growth records and the CDC growth chart.

At a clinic, further steps can be taken to determine whether there’s a problem.

Most commonly, a bone age test is done. Using an x-ray, the bones of the child are compared to the bones of other children at certain ages. What is looked for in these circumstances is that the bone age matches up to the chronological age of the child.

While girls usually continue growing until a bone age of 14, boys tend to stop growing after a bone age of 16. If the bone age in the x-ray seems to be significantly less than the chronological age of the child, chances are that the bones will continue to grow after the age that one would expect the child to stop growing.

Making Sure Your Child is on Track

What’s most important is to keep track of a boy’s height as he goes through puberty. With a solid height history and a growth chart at your disposal, it becomes easier to make sure that everything is on track.

Like any person, developing or not, it’s essential that a growing child gets a balanced diet, plenty of rest, and enough physical activity. 

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