Stages of puberty in boys – when does it begin, how does it progress, and when does it end?
Puberty is a time of intense change in a young person's body and emotions, which is why many parents wonder about the stages of puberty in boys and when this unique and, in many ways, challenging process of transforming a boy into a young man ends. Interestingly, teenagers themselves also ask many questions entered into search engines. Curious about the changes taking place in their bodies, they search for information on topics such as when a boy's penis grows, how long it takes to produce sperm, and what the penis length should be at age 14 or 16. Numerous questions about boys' puberty and issues related to both physical and psychological development also appear online. In this article, we calmly and objectively explain the various stages of puberty in boys.
When do the first stages of puberty begin in boys?
The first stages of puberty in boys usually begin a little later than for girls, most often between 9 and 14 years of ageAccording to medical standards in Poland, the average age at which the first signs of puberty appear is between 11,5 and 12,5 years of age. One of the most important signals that puberty has begun the first stage of puberty in boys, is enlargement of the testicles (so-called gonadarche) above 4 ml.
During this time, parents may also notice changes in their child's behavior, which are considered typical problems of a boy's adolescence – increased sensitivity, irritability, or a need for privacy, because adolescence in boys and the teenage psyche are strongly linked to the effects of hormones, especially testosterone.
Tanner Stages of Puberty in Boys
Tanner scale, known in the medical literature as Sexual Maturity Rating (SMR), is a classification system for objectively assessing and documenting the physical changes that occur during puberty, both in girls and boys. Thanks to it, the doctor can precisely determine what phase of development a young person is in, based on standardized criteria, which allows for monitoring stages of puberty in boysIn the case of the male reproductive system, two main parameters are assessed: degree of development of the genital organs (testicles, scrotum and penis) and pubic hairWhat do the different stages of puberty in boys look like according to a doctor?
- Stage 1: This is the pre-pubertal period, in which there are no visible changes in the structure of the genitals or hair growth.
- Stage 2: This is a crucial moment when the testicles grow to a volume of more than 4 ml or a length of more than 2,5 cm. Doctors emphasize that this is the first clinical sign of true puberty in boys, although the penis is usually not yet growing at this stage.
- Stage 3: In this phase, the testicles and scrotum continue to enlarge, and the penis also becomes noticeably longer – this is when teenagers most often enter questions like:"When do boys' penises grow?" and "What is the penis length at 14?" to check if puberty is progressing normally. Comparing oneself to others, the desire to fit in, and impress peers are among the leading problems of adolescence in boys. There's also a growth spurt and spermarche, the moment when the body can begin producing sperm.
Stages of puberty in boys according to the Tanner scale. Author: Michał Komorniczak, source: Wikimedia Commons, CC BY-SA 3.0 license
It's worth emphasizing that questions like "when do boys' penises grow" or "how long is a 15-year-old's penis?" are colloquial in nature, but they appear frequently in search engines – entered by both parents and teenagers themselves seeking information about changes occurring in their bodies. In medical terms, the proper name for this organ is the penis, but in this article, we will use both colloquial terms (e.g., penis or penis) and medical terms interchangeably. This will make it easier to explain the stages of puberty in boys while maintaining precision and clarity.
- Stage 4: It is characterized by further growth of the genitals, enlargement of the glans penis, and darkening of the scrotal skin. Voice mutation and facial hair also appear at this stage.
- Stage 5: It means reaching full physical maturity, in which the sexual organs have the size and appearance of an adult male.
Penis length during puberty – how does the penis change between the ages of 11 and 18?
Many boys search for the correct penis length for each age of puberty. However, it's worth emphasizing that the development of sexual organs occurs at a very individual pace, therefore these values should be treated as indicative.
Expert advises
Analysis of penis length during adolescence shows that although chronological age is a common reference point, the key determinant of dimensions is the stage of sexual maturity (Tanner stage). Boys of the same age may be at completely different stages of development, making the rigid "penis length per age" framework less precise than clinical assessment.
Based on research conducted on a large group of teenagers (13–15 years old), the average length of the stretched penis (stretched penile length) is as follows [10]:
- 13 years: on average 10,56 cm (with a statistical range of 9,98–11,14 cm).
- 14 years: on average 11,26 cm (with a statistical range of 11,15–11,36 cm).
- 15 years: on average 11,82 cm (with a statistical range of 11,55–12,09 cm).
For broader context, the sources also cite data from other countries, which shows the diversity of results depending on the population [10]:
- Brazil: 12 years (8,6 cm), 13 years (10,1 cm), 14 years (11,5 cm).
- Japan: 14 years (8,3 cm).
- USA (older Marshall and Tanner data): 12,5 years (12,5–14,5 cm), 14,5 years (12,5–16,5 cm).
Penis length depending on the stage of development according to the Tanner Scale described above
Because age can be misleading, doctors prefer to evaluate it by stages of genital development (G), where penis growth follows prior testicular enlargement. The average values for these stages (regardless of age) are [10]:
- Stage 1 (G1 – prepubertal): okay. 6,00 cm.
- Stage 2 (G2 – beginning of puberty): okay. 8,27 cm.
- Stage 3 (G3 – intensive growth phase): okay. 11,50 cm.
- Stage 4 (G4 – advanced stage): okay. 12,37 cm.
Important medical notes:
- Individual pace of development: Studies have shown that the penis length of boys at the same developmental stage but different ages is similar. This confirms that developmental biology is more important than date of birth.
- Measurement method: Professional measurement (stretched penile length) is taken from the pubic symphysis to the tip of the glans at maximum stretch. Self-measurements are often inaccurate.
Does the penis seem too small at age 15 or 16? What is pseudomicropenis?
In boys with excess body weight, the so-called phenomenon may occur. pseudomicropenisIn this situation, the penis may appear unnaturally small because it is partially obscured by the fat pads located above the pubic symphysis. If parents are concerned about the course of stages of puberty in boys or the appearance of your son's genitals, it is worth consulting a pediatrician.
Expert advises
A pediatrician or endocrinologist does more than just visual assessment, which can be misleading, especially in overweight children. A professional assessment often requires palpation (touch) to precisely determine the development of glandular tissue and distinguish it from fat tissue, which is important when assessing parameters such as penis length at ages 14 or 16. Specialists often use an orchidometer – a tool resembling a string of beads of varying volumes that allows for precise measurement of testicular size.
During the visit, the doctor assesses child development based on the Tanner scale and percentile charts, and will answer all your questions about the most common problems of puberty in boys.
How long does it take to produce sperm, i.e. spermarche and the first ejaculations during puberty in boys?
The moment when a boy's body starts producing sperm is medically called spermarcheMany teenagers type a question into a search engine "how long has sperm been around"because they want to make sure that the changes taking place in their body are a natural part puberty in boysThis phenomenon usually occurs between 13 and 14 years of age and most often falls on Stage 3 or 4 of the Tanner scale, i.e. the stage in which the testicles visibly enlarge, the penis grows, and the body undergoes an intense growth spurt.
Expert advises
The first ejaculation often takes the form of nocturnal emissions, involuntary ejaculations that occur during sleep. This is a completely natural symptom, indicating that boys' puberty is progressing normally and their bodies are beginning to reach reproductive maturity. The exact moment at which sperm is produced varies from person to person and depends on the pace of puberty in boys.
Puberty in boys and the teenage psyche
Adolescence is a time of profound psychological transformation for boys, in which the following come to the fore: the need for autonomy and sexualityAs young people gain increasing physical strength and intellectual prowess, they strive for independence, which often results in weakening parental authority and seeking their own place in their peer group.
During puberty in boys, the following are often observed in the teenage psyche:
- Emotional lability: Boys experience intense and often contradictory emotions, stemming from an unstable value system and neurovegetative changes. Anger and aggression may emerge as a response to frustration.
- Intellectual development: Getting educated abstract thinking fosters critical thinking, reflection, and creativity. Boys are more willing to discuss and emphasize their individuality, for example, through their clothing.
- Sexual sphere: Under the influence of androgens, it increases rapidly sexual tension and readiness for sexual response. The motivation for first intercourse is most often curiosity or the desire to fulfill expectations associated with "adulthood."
- Social Relationships and Risk: The psyche of a boy during puberty This is a profound sensitivity to one's reputation and standing among peers. This leads to a tendency to take risky actions, a love of adventure, and a need for agency.
- Identity shaping: This process involves intense self-observation and comparison with others, which may arouse fear of responsibility for life decisions.
It is worth remembering that the pace of these changes is individual, and early maturing boys, although often more popular in their peer group, may be more vulnerable to antisocial behavior and problems during adolescence.
In case of emotional difficulties, such as school anxiety or low mood (e.g. depression in teenagers), it is extremely important to have parental support, an open conversation with the child and, if necessary, consultation with a psychologist.
Puberty in boys – when does it end?
The end of puberty in boys usually occurs around between 15 and 18 years of ageDuring this time, the young body reaches its final growth stage, which is associated with the fusion of the epiphyseal cartilages in long bones. At the same time, the final stage of puberty in boys corresponds to Tanner stage 5 – the genitals and pubic hair then acquire the size and appearance typical of an adult male. However, it's worth remembering that, according to the World Health Organization (WHO) definition, adolescence, or biological and psychological maturation, lasts until the age of 19.
Expert advises
The pace of change can vary greatly, with some boys experiencing the process faster than others. However, if the first signs of puberty, such as testicular enlargement, haven't appeared by the age of 14, it's worth consulting a doctor to assess the boys' puberty stages and check for any underlying problems, such as hormonal imbalances.
Bibliography (access to internet sources as of 05.03.2026/XNUMX/XNUMX):
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- Bordini B., Rosenfield RL, Normal Sexual Development: Part II: Clinical Aspects of Puberty, "Pediatria po Dyplomie" 2012 (originally in "Pediatrics in Review" 2011). [Available online: https://podyplomie.pl/pediatria/12165,prawidlowy-rozwoj-plciowy-czesc-ii-kliniczne-aspekty-pokwitania]
- Hagenäs L., Normal and deviating puberty in boys, "Tidsskrift for Den norske legeforening" 2008. [PubMed PMID: 18511972]
- Huttunen H., Kärkinen J., Varimo T. et al., Central precocious puberty in boys: secular trend and clinical features, European Journal of Endocrinology 2024. [Available online: https://doi.org/10.1093/ejendo/lvae021]
- Klein DA, Emerick JE, Sylvester JE, Vogt KS, Disorders of Puberty: An Approach to Diagnosis and Management, "American Family Physician" 2017. [Available online: https://www.aafp.org/pubs/afp/issues/2017/1101/p590.html]
- Pomerants T., Tillmann V. et al., Ghrelin response to acute aerobic exercise in boys at different stages of puberty, "Hormone and Metabolic Research" 2006. [Available online: https://doi.org/10.1055/s-2006-955087]
- Tsinopoulou VR. et al., Puberty in boys with type 1 diabetes mellitus: What has changed?, Diabetes Research and Clinical Practice 2023. [Available online: https://doi.org/10.1016/j.diabres.2023.110837]
- Jarząbek-Bielecka G., Kapczuk K., Drejza M. (eds.), Developmental medicine – selected issues in the context of gender science, Poznań: Poznań University of Medical Sciences Publishing House, 2024. [ISBN 978-83-7597-464-5]
- Plagens-Rotman K., Jaskulska J., Bielecki M., Jarząbek-Bielecka G., Nursing care in developmental medicine [In:] Developmental medicine…, Poznan 2024.
- Soydan, Hasan & Akyol, Ilker & Ates, F. & Yilmaz, Ömer & Dursun, Furkan & Baykal, Kadir. (2012). Cross-Sectional Analysis of Penile Length in Males 13 to 15 Years Old According to Public Development Stages. The Journal of Urology. 188. 1319-23. 10.1016/j.juro.2012.06.047.
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