There are five stages of puberty, numbered 1 through 5. This classification system, called Tanner staging (also known as Sexual Maturity Rating), is what doctors use to track how a child’s body develops from the first subtle changes through full physical maturity. Stage 1 is the pre-pubertal body, and Stage 5 is the fully developed adult body.
How the Five Stages Work
The Tanner scale was designed to track specific physical changes rather than age. Each child moves through the stages at a different pace, so two kids the same age can be at completely different stages. Doctors assess the stages separately for different body areas: breast development and pubic hair in girls, genital development and pubic hair in boys. That means a child might be at Stage 3 for one marker and Stage 2 for another at the same time.
Stage 1 isn’t really “puberty” at all. It describes the childhood body before any visible changes have started. The real action begins at Stage 2, when the first signs appear, and wraps up at Stage 5, when development is essentially complete.
The Five Stages in Girls
For girls, the earliest visible sign of puberty is typically breast budding, which marks the transition from Stage 1 to Stage 2. Small, firm tissue develops beneath the nipple, sometimes on one side before the other. This often begins around age 8 to 10, though there’s a wide range of normal.
During Stage 3, breast tissue continues to grow and pubic hair becomes coarser and darker. This is also when many girls hit their fastest growth spurt. About 69% of girls reach their peak height velocity by Stage 3, meaning the growth spurt tends to happen earlier in puberty for girls than for boys.
Periods typically begin during Stage 4, around age 12 for most girls, often around the same age their biological mother or sisters started menstruating. By Stage 5, breast and pubic hair development are complete. Most girls reach their full adult height by age 16, though some continue growing through age 20. Not every girl’s pubic hair reaches the textbook Stage 5 pattern, and that’s considered a normal variation.
The Five Stages in Boys
In boys, the first sign of puberty is testicular enlargement, marking the start of Stage 2. This typically begins around age 9 to 11 and is often missed because it’s not as outwardly visible as breast development in girls. Pubic hair begins to appear as well, though doctors track genital changes and hair growth as separate indicators.
Stages 3 and 4 bring continued genital growth, voice deepening, and the growth spurt. Unlike girls, boys tend to hit their peak growth velocity later, with about 59% reaching it during Stage 4. This is why boys often seem to “catch up” in height during their mid-teens. Stage 5 marks full physical maturity, with adult genital size, body hair distribution, and muscle development. The entire process from Stage 2 to Stage 5 generally takes about four years, though it can stretch longer.
What Happens Before the Visible Changes
Before the classic signs of puberty show up, many children go through a process called adrenarche. This is driven by the adrenal glands (not the reproductive organs) and can produce body odor, oily skin, mild acne, and some pubic or underarm hair. Adrenarche can start a year or two before true puberty kicks in, which sometimes causes confusion about whether puberty has actually begun. Doctors distinguish between adrenarche and true puberty because pubic hair alone doesn’t count as a sign of pubertal onset.
When Puberty Starts Too Early or Too Late
Puberty is considered early (precocious) if it begins before age 8 in girls or before age 9 in boys. A girl showing breast development at Tanner Stage 3 by age 8 is clearly progressing rapidly and would typically be referred for evaluation. Early puberty can affect final adult height because growth plates may close sooner than expected.
Delayed puberty has its own set of thresholds. In girls, no breast development by age 12 to 13, or no period by age 15 despite other normal development, are both criteria for further evaluation. In boys, no testicular enlargement by age 13 or 14 raises the same flag. If more than three years pass between a girl’s first breast growth and her first period, or more than four years between a boy’s initial and complete genital development, that gap can also signal a problem.
The most common cause of delayed puberty is constitutional delay, which simply means a child is on a slower timeline. This runs in families and usually resolves on its own. Other causes include chronic conditions, undernutrition, or excessive exercise, all of which can temporarily suppress the hormonal signals that drive puberty forward. Children who start puberty but then stall for more than a year without progressing can be evaluated even before they hit the formal age thresholds for delayed puberty.
Why the Stages Matter
The five-stage framework gives parents and doctors a shared language for tracking development. Rather than relying solely on age, the Tanner stages let you understand where a child is in the process and what to expect next. A boy at Stage 3 with no growth spurt yet, for instance, isn’t necessarily behind. Most boys don’t hit their fastest growth until Stage 4. Knowing the stage helps set realistic expectations and identify when something genuinely needs medical attention versus when a child is simply on their own schedule.