When do boys stop growing? Most boys will be done growing by age 17 or 18. Learn about puberty in boys, including boys puberty stages, how the growth spurt in boys unfolds, and when boys fully mature.
One of my most popular posts, 13 Signs of the Teen Growth Spurt, teases the answer to a question I get all the time: What age do boys stop growing?
I get this question about girls, too.
As a pediatric nutritionist and a mom, I know that growth spurts are individualized. While we have growth norms and Tanner stages, each individual child marches through puberty on their own time table.
Boys Puberty Stages
I have a permanent memory of a photo I saw long ago (I wish I could find it!) of 20 or so 17- year-old male teens lined up.
The boys were ordered by height, from shortest to tallest. The boys on the shortest end looked like young middle school boys, while the teens on the tallest end looked like full-grown men.
This photo was a good representation of the wide variability in growth for boys as they go through puberty.
Girls aren’t quite so dramatic in their growth. I cover what age girls stop growing and other facts about puberty for girls so you know what to expect.
In this article, we’ll explore puberty in boys, the process they go through, and how to know when males stop growing, reaching their full adult height.
The First Sign of Puberty in Boys
Puberty doesn’t happen without a surge in hormones. For boys, that means a rising level of testosterone. This elevated hormone spurs the physical changes we see during the growth spurt in boys. This happens generally between ages 9 and 14.
The first sign of puberty in boys is the enlargement of the testicles. Physical changes happen in the following areas:
- The testicles and scrotum
- Pubic hair
- Body shape changes
- Penis growth
- Voice changes
- Breast Development
Growth of the Testicles and Scrotum
During pubertal growth, these almost double in size. The skin of the scrotal sac thins, darkens, and the testicles hang lower. Hair follicles (bumps on the scrotal sac) appear.
Pubic Hair Development
Hair begins to grow at the base of the penis and darkens. Throughout puberty, this hair grows in a diamond pattern and spreads to the upper thighs and up to the belly button. Pubic hair grows prior to face, arm, leg, underarm, and chest hair.
Body Composition Changes
Boys appear thicker and heavier during the mid-teen years, right before puberty begins. Of course, some boys won’t look chubby at all.
The growth spurt happens for boys during the later stages of maturation. Boys layer on muscle (as opposed to girls layering on fat to their body composition) at this time.
Boys end physical maturation with 12% body fat on average.
Growth of the Penis
The penis grows in length first, then becomes thicker. Boys can develop an adult size penis as early as age thirteen and up to age eighteen.
The voice box and vocal cords get bigger after the peak of the growth spurt. You’ll know this is happening as your son’s voice may crack.
This ends when the voice box is fully grown.
Yes, boys develop breast tissue too. In fact, it’s quite common for boys to have breast buds during puberty.
This is due to the hormone testosterone converting to estrogen (the female puberty hormone), through a chemical reaction in the body.
If your son has a firm breast bud under the nipple, this is why. It is called gynecomastia.
Gynecomastia typically resolves within one to two years. However, if gynecomastia occurs prior to puberty or late in the teens years, check in with your doctor.
Tanner Stages in Boys
The Tanner stages in boys represent two areas of sexual maturation: pubic hair and genital development. It allows your doctor to determine where your son falls along his pubertal development and adult maturation.
There are 5 stages beginning with Stage 1 (which means there is no sign of puberty) to Stage 5 which translates to full adult growth.
Doctors take these Tanner stages into consideration along with your kid’s growth to determine progress in physical maturity.
Review of Tanner Stages in Males
|Tanner Stage||Pubic Hair||Genital Development|
|Stage 1||No hair at all||Testicular volume is |
less than 1.5 ml; small
|Stage 2||Downy hair with slight pigmentation||Testicular volume 1.6 – 6 ml; penis length |
|Stage 3||Scant dark hair; coarse and curly||Testicular volume 6 –|
12 ml; penis lengthens
|Stage 4||Hair that fills the |
around the genitals
|Testicular volume 12-|
20 ml; penis lengthens
|Stage 5||Hair that extends |
beyond the genital
area onto the thighs
|Testicular volume greater than 20 ml; adult |
scrotum and penis
The Male Growth Chart
The Centers for Disease Control and Prevention (CDC) has growth charts for girls and boys, aged 2 to 20 in the U.S.
Growth charts track weight, height and body mass index (BMI) over time.
The pattern of growth and percentile channel your child grows along is a good indicator your child is growing normally.
Also, it helps to get a sense of what to expect with your teen’s development. There are a lot of changes happening with social and emotional development, too!
Average Boy Height Based on Age
On the growth chart, the 50%ile is considered the “average” height for a boy at a particular age. In other words, it is the mean height for age.
However, height varies widely, with some boys growing at the 5% ile for height, at the 95%ile for height, and at many percentiles in between. Your son’s height is influenced by his genetic makeup.
- Average Height for a 9 year old boy 52”
- Average Height for a 10 year old boy 54.5”
- Average Height for a 11 year old boy 56.5”
- Average Height for a 12 year old boy 58 2/3”
- Average Height for a 13 year old boy 61.5”
- Average Height for a 14 year old boy 64.5”
- Average Height for a 15 year old boy ~67”
- Average Height for a 16 year old boy 68 1/3”
- Average Height for a 17 year old boy 69”
- Average Height for a 18 year old boy 69 1/3”
Height Calculator for Teenagers
The growth chart is one of the best predictors of final adult height. Follow your child’s height normal growth percentile (the channel where he’s actually been growing) to age 20 (the end of the curve) for a rough estimate of his final height.
Alternatively, you can use a common calculation based on combining parent heights and factoring in variances for males and females. Check out this height predictor tool in 7 Ways to Support the Teen Growth Spurt.
Average Weight in Boys
The weight of your son can be tracked on the growth chart, too. While height is influenced (strongly) by genetics, your son’s weight has more to do with eating habits, food choice, physical activity and more.
Read my Healthy Living Series to understand all the influences on your child’s weight.
Yes, there can be a genetic influence, particularly with a tendency toward overweight and obesity, however, your son’s eating environment and lifestyle habits set the foundation for weight and health.
My nutrition class, The Nourished Child Project, can help you set (or re-set) the food environment, feeding practices and healthy habits your child needs to grow up healthy, inside and out.
Growth Spurts in Boys
The growth spurt in boys is the peak of growth during adolescence. It follows the beginning of puberty, typically starting around age 14 or 15 and ends around age 17 or 18.
It’s an intensive three years! Of course, every boy is different. Some boys begin the growth spurt earlier and others later.
Early Puberty for Boys
Early puberty, or precocious puberty, begins before age 9 in boys. It occurs when the hypothalamus in the brain signals the secretion of testosterone.
As a result, the physical changes including body odor, pubic hair, penile growth, acne, facial hair, voice changes and rapid height growth happen earlier than expected.
Precocious puberty is less common in boys than girls. Boys who go through early puberty may not reach their adult height potential if left untreated. Talk with your doctor if you suspect your son has signs of early puberty.
A Late Growth Spurt
Some boys are late bloomers, entering puberty later than expected. If puberty hasn’t started by age 14, it is called delayed puberty. Your doctor can help you decide how to manage this, if at all.
Signs Your Son Has Reached Full Height
If you follow your son’s growth chart you’ll see it begins to flatten out around age 18 -20, indicating linear growth is slowing down and full adult height is likely.
However, boys who enter puberty later may continue to grow into early adulthood.
What Age Do Boys Stop Growing?
Every boy has on his own trajectory with growth. It’s hard to say when adult height will be reached. Most will be done by age 17 or 18, however, some will continue to grow into the early 20’s.
However, if you stay informed about your son’s growth and development over time, you will begin to notice his patterns and get a sense of where he’ll end up, height-wise.
- Physical Development in Boys: https://www.healthychildren.org/English/ages-stages/gradeschool/puberty/Pages/Physical-Development-Boys-What-to-Expect.aspx
- CDC Growth Charts: https://www.cdc.gov/growthcharts/index.htm
- Delayed Puberty: https://www.healthychildren.org/English/ages-stages/gradeschool/puberty/Pages/Delayed-Puberty.aspx