What Happens During Puberty in Boys?

Most boys begin puberty between ages 9 and 14. The first true sign is enlargement of the testicles, not a deeper voice, facial hair or a sudden jump in height. The biggest growth spurt comes later, usually about two years after puberty begins, and the voice deepens around or after that peak.

That order matters more than the calendar. Two healthy 13-year-olds can look completely different because one started puberty two years ago and the other is just beginning.

LIFE Pediatric Endocrinology is a national pediatric endocrinology practice caring for children and teens with growth, puberty and hormonal concerns. We evaluate growth and puberty together because where a boy is in puberty explains a great deal about his current height and the growth that may still be ahead.

When Does Puberty Start in Boys?

About 95% of boys start puberty between ages 9 and 14. The average onset is around age 11½, but there is considerable normal variation.

Genetics shape much of the timing. A boy whose father had a late growth spurt or continued growing later than his peers may follow a later pattern himself.

This wide range is why age alone is a poor yardstick. A 13-year-old who has been in puberty for two years is at a very different biological point than a 13-year-old who is just starting, even though they share a birthday year.

Age tells us part of the story. Sequence, tempo and growth velocity often tell us much more.

What Is the First Sign of Puberty in a Boy?

The first true sign is enlargement of the testicles.

It happens when the brain and pituitary gland increase their release of two hormones, LH and FSH, which signal the testicles to grow and produce more testosterone.

Physicians generally consider a testicular volume of approximately 4 mL or more as evidence that puberty has begun.

Because this change can be easy for families to miss, many parents don't realize puberty has started until later signs appear.

For more detail, see LIFE's guide to what a testicular volume of 4 mL means for boys and puberty.

What Are the Signs of Puberty in Boys?

Puberty unfolds over several years, and the changes arrive gradually. Parents may notice:

• Body odor and oilier skin or acne
• Pubic hair, followed later by more underarm, leg and facial hair
• Enlargement of the testicles and penis
• Faster height growth, followed by the main growth spurt
• Broader shoulders and increasing muscle
• A voice that cracks and then deepens
• Tenderness or a small amount of breast tissue beneath one or both nipples
• Changes in mood, independence and privacy

Not every sign means the same thing.

Body odor, acne and some pubic or underarm hair can come from adrenarche, a rise in adrenal hormones that is separate from true central puberty and can begin a year or two earlier.

These changes alone do not confirm that puberty has started. Testicular enlargement is the more reliable marker, which is one reason a clinical examination can answer questions that a checklist cannot.

Is Breast Development Normal During Puberty in Boys?

It can be.

Temporary breast tissue development, called pubertal gynecomastia, occurs in roughly half of adolescent boys and is particularly common during the middle stages of puberty. In many cases, it gradually resolves on its own within one to two years.

Breast development before puberty, rapid or unusual enlargement, persistent gynecomastia or other concerning symptoms should be evaluated.

What Are the Stages of Puberty in Boys?

Physicians describe puberty in five Tanner stages, also called Sexual Maturity Ratings:

Stage 1: No pubertal changes yet.

Stage 2: Puberty begins. The testicles enlarge, and the first pubic hair may appear.

Stage 3: Development continues and height growth speeds up. The growth spurt often peaks during stage 3 or stage 4.

Stage 4: Pubertal development continues. The voice deepens, facial hair becomes more apparent and muscle development increases.

Stage 5: Physical development is essentially complete, and height growth slows toward adult height.

One of the most important things for parents to understand is that the fastest height growth usually occurs during the middle stages of puberty—not at the beginning.

Tanner staging is done by a physician during a clinical examination. Parents do not need to stage their son at home.

What helps more is noticing the bigger picture: Has puberty begun? Are changes continuing over time? Is his height picking up as expected?

For more, see LIFE's guide to Tanner staging and bone age.

What Is the Typical Sequence of Puberty in Boys?

The order of puberty is more predictable than its timing. In most boys it progresses something like this:

1. The testicles enlarge.
2. Pubic hair appears and genital development continues.
3. Height growth begins to accelerate.
4. The growth spurt peaks, usually during the middle-to-later stages of puberty.
5. The voice deepens around or after the peak growth period.
6. Facial and body hair continue to develop, and muscle mass increases.
7. Height growth slows and eventually stops.

The typical sequence of puberty in boys: Puberty usually begins with testicular enlargement, followed by increasing body hair and other physical changes. Height growth then accelerates, with the major growth spurt occurring in the middle-to-later stages of puberty. Voice deepening and increased muscle development generally follow as boys progress toward physical maturity. 

The most common surprise for parents is step four.

Puberty can be well underway before a boy suddenly gets taller because the biggest height gains usually come during the middle-to-later stages. A son who has started puberty but hasn't had his major growth spurt yet may still be progressing exactly as expected.

When Do Boys Have Their Biggest Growth Spurt?

Most boys reach their fastest period of growth about two years after puberty begins.

Peak height velocity typically occurs during Tanner stages 3 to 4, at an average age of approximately 13½. Because the timing of puberty varies considerably, the timing of the growth spurt varies too.

That explains the classic middle-school photo: some boys are already in their peak growth year while classmates the same age have not reached it.

Neither is necessarily ahead or behind. They may simply be at different points in the same developmental sequence.

How Much Do Boys Grow During Puberty?

At peak growth, boys gain about 3½ to 4 inches per year on average.

Across puberty as a whole, boys add roughly 12 inches of height on average, although individual growth varies considerably.

Those numbers describe populations, not individual predictions.

For an individual child, the pattern matters more.

Pediatric endocrinologists pay close attention to growth velocity, meaning how quickly a child gains height over time. Two boys can both stand 5 feet tall, but if one grew 4 inches last year and the other grew 1½ inches, their growth patterns tell very different stories.

A boy's height tells us where he is today.

His growth velocity helps tell us where his growth is going.

How Long Does Puberty Last in Boys?

Puberty in boys usually takes about three to four years from its first true signs through the later stages of physical maturation.

Both the starting age and pace vary. Some boys move through the stages relatively quickly, while others progress more gradually and still develop normally.

This is another reason comparing boys with classmates can create unnecessary concern. Even a relatively small difference in pubertal timing can produce a very visible difference in height, muscle development, voice and overall appearance.

When Does Puberty End for Boys?

There is no single age.

Boys who start earlier generally finish earlier, while boys who start later may continue developing into their later teenage years.

Different changes also finish at different times. Height may be nearing completion while muscle development, facial hair and body hair continue to mature.

A more useful question than:

“What age does puberty end?”

is:

“Where is my son in his own pubertal sequence?”

That answer tells us much more about what may happen next.

When Do Boys Stop Growing?

Boys stop growing when their growth plates mature, which occurs as pubertal development advances toward completion.

Boys who start puberty earlier often finish growing earlier, while later-maturing boys may continue growing longer.

Age alone cannot tell you how much growth remains. Pubertal stage, growth velocity, genetic growth potential and sometimes a bone age can provide a much clearer picture.

Is It Normal for a 13-Year-Old Boy Not to Have Started Puberty?

Often, yes.

Normal male puberty can begin as late as age 14, so a 13-year-old who has not clearly started puberty is not automatically outside the expected range.

But age is only one piece of the picture.

Slow height growth, falling across height percentiles or being much shorter than expected based on the family's heights are reasons to look more closely rather than relying on age alone.

What If My Son Is 14 and Hasn't Started Puberty?

Physicians consider puberty delayed when a boy has no testicular enlargement by age 14.

That is a clinical definition—not a diagnosis.

Constitutional growth delay, often called the classic “late bloomer” pattern, is one of the most common causes of delayed puberty in boys and frequently runs in families.

Time may ultimately be all a healthy late bloomer needs.

But waiting alone doesn't tell you whether that is actually your son's pattern.

A pediatric endocrine evaluation can help distinguish constitutional delay from a hormonal, nutritional or other medical reason puberty has not begun and give the family real information instead of guesswork.

Read more in Delayed Puberty in Boys: Signs, Causes & When to Evaluate.

What Can Affect the Timing of Puberty?

Genetics play an important role, but they are not the only influence.

Overall health, nutrition, sleep, energy availability, chronic illness, intense physical training, thyroid function and other hormonal or medical conditions can influence when puberty starts or how it progresses.

Many later-developing boys will not have an underlying endocrine disorder.

That is precisely why an evaluation focuses on the whole growth and developmental pattern, rather than one age or one measurement.

Can Puberty Start Too Early in Boys?

Yes.

Signs of true puberty before age 9 in a boy are considered precocious puberty and warrant medical evaluation.

Early puberty is less common in boys than in girls and can be associated with an underlying medical cause, making appropriate evaluation particularly important.

Early puberty can initially make a boy look tall for his age because sex hormones accelerate growth.

Those same hormonal changes also advance skeletal maturation.

A boy can therefore grow quickly now while moving more quickly through the developmental window available for future height growth.

It's another reason height should never be interpreted without understanding where a child is in puberty.

How Does a Pediatric Endocrinologist Evaluate Puberty?

An evaluation starts with the child's story and his growth chart.

A pediatric endocrinologist reviews several years of height measurements, growth velocity, parental heights and family pubertal timing, along with a physical examination to determine whether puberty has begun and how far it has progressed.

A bone age X-ray of the hand and wrist or targeted laboratory testing may be added when they answer a specific clinical question.

Not every child needs every test.

And an evaluation does not automatically mean treatment.

The goal is first to understand whether the child's growth and puberty make sense for him.

When Should Parents Consider a Puberty Evaluation?

Consider a pediatric endocrine evaluation if your son:

• Shows signs of true puberty before age 9
• Has no testicular enlargement by age 14
• Has height growth that has slowed unexpectedly
• Is dropping across height percentiles
• Started puberty but does not seem to be progressing
• Is much shorter than expected based on family height
• Is significantly distressed by how his growth or development compares with peers

Often, the most valuable result is simply clarity: knowing where your son is in his development, whether his pattern makes sense and what to expect next.

Frequently Asked Questions About Puberty in Boys

What age does puberty start for boys?

Most boys start puberty between ages 9 and 14, with average onset around age 11½. Two healthy boys of the same age can therefore be at very different stages of development.

What is the first sign of puberty in a boy?

The first true sign is enlargement of the testicles. Voice changes, facial hair and the main growth spurt generally occur later.

Does body odor mean my son has started puberty?

Not by itself. Body odor, acne and some pubic hair can result from adrenal hormones before true central puberty begins. Testicular enlargement is the more reliable clinical marker.

When do boys have their growth spurt?

The peak growth spurt usually occurs about two years after puberty begins, during the middle-to-later stages of puberty.

How much do boys grow during puberty?

At peak growth, boys average roughly 3½ to 4 inches of height per year. Across puberty as a whole, boys add approximately 12 inches on average, although individual growth varies substantially.

How long does puberty last for boys?

Usually about three to four years, although boys differ in both when puberty begins and how quickly they progress.

When is puberty considered delayed in boys?

Puberty is considered delayed when there is no testicular enlargement by age 14. Constitutional growth delay is a common explanation, but an evaluation is how families determine whether the pattern is truly that of a healthy late bloomer.

When is puberty considered too early in boys?

Signs of true puberty before age 9 are considered early in boys and should be evaluated.

Understand Your Son's Growth and Puberty

If your son's puberty timing, growth or height potential raises questions, an individualized pediatric endocrine evaluation can provide a clearer picture of where he is now and what may come next.

LIFE's physicians evaluate growth and puberty together, looking at the complete developmental pattern rather than one height, one percentile or one birthday.

Contact LIFE Pediatric Endocrinology →

About Dr. Payal Patel

Payal Patel, MD, is a board-certified pediatric endocrinologist at LIFE Pediatric Endocrinology, where growth and puberty are a flagship focus of her practice. She joined LIFE after practicing with Phoenix Children's and Banner Health in Arizona and has particular experience guiding children through growth and puberty after cancer treatment.

Her approach pairs evidence-based pediatric endocrinology with close attention to nutrition, sleep, lifestyle and each family's individual goals.

Read Dr. Payal Patel's full bio →

References

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5. Bakhtiani P, Geffner M. Early Puberty. Pediatrics in Review. 2022;43(9):483–492. doi:10.1542/pir.2021-005059. American Academy of Pediatrics
6. Abbassi V. Growth and Normal Puberty. Pediatrics. 1998;102(Suppl 3):507–511. doi:10.1542/peds.102.S3.507. American Academy of Pediatrics
7. Granados A, Gebremariam A, Lee JM. Relationship Between Timing of Peak Height Velocity and Pubertal Staging in Boys and Girls. Journal of Clinical Research in Pediatric Endocrinology. 2015;7(3):235–237. doi:10.4274/jcrpe.2007. PubMed
8. American Academy of Pediatrics and Pediatric Endocrine Society. Delayed Puberty in Boys: Information for Parents. HealthyChildren.org. HealthyChildren.org
9. Pediatric Endocrine Society. Delayed Puberty in Boys: A Guide for Families. Published June 17, 2020.

Medical Disclaimer

This article is for educational purposes only and does not replace individualized medical advice, diagnosis or treatment. Growth and pubertal development vary from child to child. Families with concerns about a child's growth or puberty should seek individualized guidance from a qualified healthcare professional.