Puberty is when your body begins making rapid changes from childhood into manhood. The years of these changes are called adolescence, which literally means growing up. The exact time that puberty begins varies widely from one person to the next. On average, puberty starts around age 12, though it is not unusual for some boys to begin changing as early as age 10 or as late as age 15.

The changes to your body do not occur overnight. It takes many years for your body to change from a boy to a man fully. On average, these changes take place over an eight to ten-year period. As with the start of the changes, the duration of the changes varies from person to person. Most of your height will be gained during your teenage years. However, it is not usual for men to add another inch or so to their height after they reach 20.

As boys approach their teenage years a series of chemicals, called androgens are released into the bloodstream. Androgens are male hormones (female hormones are called estrogens). The main androgen is called testosterone. Testosterone is manufactured in the testicles and is released in the bloodstream in large quantities about a year before you see physical changes in yourself.

The order of changes varies among individuals. Some boys first realize that they have entered puberty when they notice that their genitals have begun to get larger. Other boys first notice puberty when they experience a spontaneous erection. Still, other boys first realize they have entered puberty when they have their first ejaculation. It is not unusual for the first sign of growing up to be hair growth around the genitals or a rapid gain in height.

You will notice many changes over the next 10 years or so. They will not occur all at once and will not last for all of your teenage years. Some changes will affect you deeply, and some changes you will hardly notice. It varies from person to person.

Increased appetite: Testosterone causes your body to grow, and that growth needs additional energy. You will consume a large quantity of food over the next few years. You will be looking for a snack just hours after your last meal. Your parents will wonder how they can afford the next grocery bill. All of this is normal for a teenage boy. Just don’t let it become a permanent habit. Once your growth stops, all that extra food will be stored as fat. This is why many men become chubbier as they grow older.

Mood swings: Testosterone also causes extremes in moods. If you become angry, you find yourself very angry. Depression sometimes strikes, and you find yourself weeping over silly things. These extreme moods happen because your body is trying to adjust to the new hormone levels in your blood, and at times, the body overreacts to your thoughts. Some describe the effect of hormones as an amplifier of emotions. During your adolescent years, your hormone levels will not be steady. The regulatory systems over or underproduce while trying to reach the right level. Eventually, as you near the end of adolescence, your hormone levels will reach a steady level that will be roughly maintained the same throughout the rest of your life.

At the same time, your brain is developing. Different sections of the brain are responsible for various things. During adolescence, the section of your brain that reacts emotionally is well developed. However, the part of your brain responsible for tempering your emotions with reason is still under development. This will settle down as you become older. The section that tempers your emotions is one of the last centers to be completed. Meanwhile, learn to expect that you will overreact to situations and try to keep your emotions under control.

As Christians, we must be sober and self-controlled (I Peter 4:7; I Corinthians 9:25). Too many teenagers let their emotions run wild. They read things into situations that are not actually there. After it is too late, they wonder why they lashed out at someone in anger or contemplated suicide when they were depressed.

Sleepiness: The extra energy you expend on growing will cause you to sleep longer than you have in the past. It doesn’t help when you find your days packed with more things to do so that you crash for most of the morning when the weekend finally comes. It may be hard but try to keep a regular schedule and allow yourself adequate time to rest.

Growth: Your body will rapidly change in size. For most boys, the bulk of the growth will occur about a year after you enter puberty (between the ages of 13 and 14). Clothes that fit you last week will suddenly be too short this week. The growth starts with your feet and hands, moves to the legs and arms, and finally extends to your trunk as you fill out and lengthen. The growth will come in spurts over the next 10 years. Even after you have completed college, you may have added another inch to your height.

A difficult part about growing is adjusting to the new length. You will stumble because your foot is now a few inches longer than it was in childhood. The length of your stride changes as well. Suddenly, you find yourself having to learn how to walk all over. As your arm lengthens, you will frequently knock things over. The glass you see on the table is no longer as far as you remember it being because your arm is longer. Several spilled drinks will be in your life over the next few years.

This clumsiness is temporary, so give yourself time to adjust to your new size. Be a little more conscientious about your movements—where you put your hands or where you place your feet. Doing things by habit can get you into trouble because you are making child-size movements with an adult-size body.

One area of change that affects most boys is the temporary swelling of the breasts. The swelling may be accompanied by tenderness in that area. Don’t become concerned; it will pass in about a year to a year and a half.

Muscles: Testosterone dramatically affects the development of muscles. Men have more muscle mass than women because more testosterone flows through their bodies. Most muscle growth will occur during the latter half of your teenage years. As you can lift heavier and heavier loads, be careful not to overdo it. Rapidly growing muscles can be easily damaged.

Your increased strength will cause some awkwardness over the next few years. One day, you may pick up an egg and find it shatters in your hand. You need to relearn the proper amount of strength necessary for each task. I remember helping my Dad change a tire on our trailer and breaking the bolt as I tightened the lug nuts. It never occurred to me that I was strong enough to break a metal bolt. The clumsiness from being too strong will diminish as you adjust to your new-found strength. By the way, you may notice that girls don’t seem to like to hold your hand. It may be because you are cutting off the circulation in their hands, so relax a little.

Hair: Soon after puberty begins, you will notice small bumps on your skin around your groin. Looking closely, you may see fine hair growing in the center of each bump. This is the beginning of curly pubic hair that grows around your genitals. Later, the hair will grow under your arms and over other body regions, such as on your legs, arms, and face. A final area for hair to appear is on your chest. Your genes determine the amount and thickness of your hair. Some men will be very hairy, with hair growing thickly over their bodies. Other men will have thick patches of hair in certain areas of their bodies. Still others will have very little body hair. Each pattern of hair growth is normal.

As the hairs grow, they tend to get caught and pulled in loosely woven material, such as knit pants. This is often painful, like someone pinching you, and it seems to happen regularly when you can’t do anything about it without people seeing you.

Facial hair begins to grow around 15 or 16 years of age. At first, the hair is light and grows slowly. You can probably get by shaving only once or twice a week. Later, it will come in darker and more quickly. Some men, especially those with lighter-colored hair, will still be able to shave infrequently. Those of you with darker hair may find yourself needing to shave at least once a day.

Acne: With increased growth, your skin produces an abundance of oil, more than you had during your childhood. For many people, the glands that produce the oil become clogged with dirt or dried oil. This causes the oil to back up underneath the skin and become inflamed. The inflammation is called acne. Some teenagers get acne very severely, and a few lucky ones will rarely experience it. For most of you, wash your face and areas where it appears thoroughly with soap and a washcloth. This will help to free the clogs and keep down the excess oil. Even this will be inadequate for some people, and you may need to see your doctor for additional treatment if you find it embarrassing. A few people prone to scaring will develop small scars on their faces. The scars are due to how the skin heals when the skin over the clogged oil glands breaks. These people will want to control their acne tightly since the scarring is usually permanent.

Grown men still occasionally have a pimple show up now and then. However, you will be happy to know that acne occurs less frequently after your growth stops and your body adjusts to the new hormone levels in your blood.

Men with curly or kinky hair (usually of a Mediterranean or African heritage) have a problem with some of their hair curling before it grows out of the hair follicles. The skin around the trapped hair becomes red and may become infected. Unlike acne, the centers of this inflammation are black instead of white. Treatment for this problem is the same as for acne. Keeping your skin pores clean leaves more room for hair to exit their follicles properly. A clean face also reduces infections.

Sweat: Like your oil glands, you will soon discover that your sweat glands will also work overtime. Growing causes your body to produce excess heat. When others pull on extra sweaters, you may find the temperature warm. The excess heat and the fluctuating hormone levels in your blood will often cause you to sweat readily and profusely. As with acne, once your growth spurt stops, your body will no longer produce as much sweat.

Deepening Voice: Along with other changes, your vocal cords lengthen, giving you a deeper voice. The change begins around the age of 14. The change does not occur smoothly, as with all the other changes that will be happening. As you speak, your voice will make sudden changes in pitch. One moment, your voice is deep and manly, and the next moment, you are squeaking like a mouse. This frequently occurs when you get excited and do not consider keeping your voice even. It is embarrassing to see yourself squeaking periodically and just when you gain a manly voice, but it happens to everyone. Your body has to relearn how to speak – compensating for the changes in your voice box.

Genitals: All the changes that we have talked about happen gradually over many years, and the genitals are no exception. The first change to occur is the growth of the testes and the scrotum. This growth is the official start of puberty, but it happens so gradually that most boys don’t notice it. Your testes continue to grow larger throughout adolescence. In addition, the shaft of the penis will lengthen and widen. A more noticeable physical change to the genital area is hair growth around the genitals.

About a year after puberty officially starts, an event that stands out in every man’s mind is when he leaves childhood and starts on the road to manhood. At some point, each of you experienced a lengthening and stiffening of your penis, which is known as an erection. Most boys have mild erections from the time that they are born. However, these early stiffenings of the penis are so minor that most boys never notice them. The penis barely lengthens or widens with these early erections. The erections after puberty are much more dramatic. Your penis lengthens from two to three inches to three to seven inches in length, and the width of your penis doubles. For most of you, a release of semen, a thick whitish liquid, accompanied your first full erection. The semen that leaves your penis is also called ejaculate. Until this point in your life, sex was some dumb thing that other people talked about and did. Now, you suddenly realize that it is relevant to you as well.

The most embarrassing thing about having an erection is that it keeps occurring. It is as if you have no control over this body part. In a sense, you don’t. If you have ever seen a newborn child, its legs and arms move aimlessly through the air. A baby may see a toy, and his legs and arms will move excitedly, but at first, it cannot make them reach it. The body needs time to associate thoughts with movements of the arm. To fully develop this capability takes years.

Having erections is a new “movement” for your body. At first, just about anything and everything triggers an erection. A thought may trigger erections, something you see or read, a touch, or the rubbing of your clothing on your penis. Erections can also be triggered just by being excited or nervous. Sometimes, nothing in particular will be happening, but you still have an erection. These spontaneous erections happen at different rates for different people. Some boys only experience a spontaneous erection occasionally. Other boys find themselves having erections multiple times each day.

From puberty to the end of your life, you will experience erections at night as you sleep. Unless there is something physically wrong with your body, you will normally have three to four erections each night. Since they happen while you sleep, you won’t notice them often. A lack of night erections may be an indication that there is something physically wrong with your body.

Over time, your body will learn to adjust, and the erections will become a bit more controllable. Fewer things will trigger an erection, and at times, you probably can resist an erection by conscientious thought. Just remember that it will take years for the adjustment to come about. Meanwhile, expect to have erections at inopportune times. Since nervousness can trigger an erection, it is not unusual to find yourself having one when you are giving a presentation before an audience. Try not to let it bother you too much. You know it is happening because you can feel the pressure against your pants, but most people around you will never notice.

Plan on having frequent erections for many years (even into your twenties). When putting on your underwear, position your penis pointing upwards so that when an erection does occur, your penis does not try to push your pants outward. An upward direction is also more comfortable. During an erection, your penis will lengthen to five to seven inches; most pants won’t stretch that far. When your penis is flaccid (or limp) and pointing downwards, having an erection is very uncomfortable as your penis tries to straighten upwards with nowhere to go. Even with the best preparation, there are going to be times when you must excuse yourself and find a private place to reposition your penis.

Stages of Development: Several years ago, a doctor, Dr. Tanner, divided growth into five stages. These stages, known as the Tanner Stages, help doctors quickly determine how far a child has sexually matured. For boys, the stages are determined by the development of the external genitals.

Stage 1: This is the stage every child is in before puberty. A child’s height increases by about 1 to 2 inches each year. His genitals are those of a child: there are no pubic hairs, and the scrotum is small and up close to the body.

Stage 2: This stage begins when a child enters puberty. The typical boy reaches puberty between the ages of nine and a half and fifteen, with the average age being eleven and a half. As mentioned earlier, it is normal for a boy to start as early as nine or as late as sixteen.

A boy’s height continues to increase at the childhood rate of 1 to 2 inches yearly. Two changes to the genitals begin but are often overlooked: the testes begin to swell, and the penis begins to lengthen just slightly. Spontaneous erections begin during this stage. About six months later, hair will begin to appear at the base of the penis. The first ejaculation occurs during this stage for about half of all boys.

Most boys begin to look chubby during this stage as their bodies lay down fat to help fuel future growth. About half of all boys experience breast swelling.

Stage 3: This is the stage where most boys notice they are changing. It usually starts about two years after the beginning of stage 2. The typical boy will reach this stage between the ages of eleven and sixteen, with the average age around thirteen.

A boy’s growth in height accelerates to double the childhood rate or more, adding 2 to 4 inches each year. Most of the growth is in the legs, giving a teenager’s typical “leggy” proportions. The testes continue to grow. Now, the scrotum is large enough that it gives the appearance of hanging down. The penis grows mainly in length but also increases in width a bit.

Pubic hair, around the genitals, thickens – becoming coarse and curly. The hair also spreads, covering most of the flat area (the pubis) between the legs. Leg and arm hair also begin to grow. Some hair may start to grow around the anus. Hair in the armpits may begin to appear.

The areola, the dark area around the nipples, begins to darken and become more noticeable. During this stage, the voice begins to change, causing it to break or squeak.

Stage 4: This stage begins when a boy’s growth rate declines back to his childhood rate or less. It generally begins about two years after stage 3 is reached. The typical age is between twelve and seventeen, with the average being around fifteen. From this point, the growth rate slows down, and instead, the shoulders widen, and muscles begin to develop.

The testes continue their growth. One testicle, usually the left, is noticeably lower than the other. The penis continues to grow, but now it is mostly in width instead of in length. The glan at the end of the penis begins to enlarge. If ejaculations hadn’t started earlier, they would definitely have begun during this stage.

The pubic hair continues to become denser and reaches from thigh to thigh. Many boys develop a narrow strip of hair that goes from the genitals up to the navel (belly button). Hair in the armpits becomes noticeable during this stage. Facial hair begins to develop on the upper lip and chin. And the scourge of teenagers – acne – begins to appear.

The nipples become distinct and stand out from the areola. During stage 4, the voice settles down to its adult pitch.

Stage 5: While all growth hasn’t completely stopped, by stage 5, the boy has an adult-shaped body and has reached his adult height. The shoulders continue to widen as muscles further develop. The genitals have reached their full adult size and shape. Stage 5 is reached about two years after stage 4 begins. The typical age is between thirteen and eighteen, with the average being about seventeen.

The pubic hair now covers the entire groin region and is present on the inside thighs. Facial hair is now thicker and might necessitate regular shaving. Chest hair begins to grow. The hairline at the temples recedes a bit.

To estimate what stage of development you are in, see the Tanner Stage Calculator for Boys.

Mental: As you live, you learn more things, but as your body develops, what you can learn also develops. When you were a small child, the earliest areas to mature in your brain were those that govern smell, hearing, and sight. Next came the areas governing movement and touch. Then, you develop language abilities and the ability to get your bearings based on the coordinated use of your senses. The section that controls reasoning and decision-making is one of the last areas to develop. For boys, these areas do not fully develop until their early twenties.

This is one of the reasons car insurance is higher for young men. Your ability to look at a risky situation and make safe decisions is not fully functional. Young men are willing to take risks that older men will avoid. Yet, the greater risks mean you are more likely to do something damaging to yourself or others. For young men, it becomes critical to listen to the advice of older, more experienced adults. “Hear, my son, and receive my sayings, and the years of your life will be many. I have taught you in the way of wisdom; I have led you in right paths. When you walk, your steps will not be hindered, and when you run, you will not stumble. Take firm hold of instruction, do not let go; keep her, for she is your life” (Proverbs 4:10-13).

Study Questions

1. When did you first notice that you had reached puberty?
2. List seven things that will change as you go through adolescence.
3. What is testosterone?
4. What causes spontaneous erections?
5. When do many boys begin to shave?
6. Why is it that two 13-year-olds will be at different points in their maturation even though they are the same age?
7. What causes clumsiness in teenagers?
8. Why do teenage boys’ voices squeak?

Class Discussion

• When did you first notice that you had reached puberty?
• What problems have spontaneous erections caused you?
• When did you begin to shave?
• Has clumsiness been a problem?
• Did your voice change cause you problems?
• Did you have problems with temporary breast swelling?
• How did you handle being teased because of changes to your body?

How Tall Will I Be?

Because of the frequent requests for estimates on how tall a person will be, I added a page that contains calculators to predict your adult height. Click on the question above to do your own estimates.

Tanner Stage Calculator for Boys

It seems that many wonder what will happen next: Am I still growing, is my penis going to get bigger? Have I started puberty yet? This page asks several questions and estimates at what stage in development that you are in.