Puberty Timing & Growth
Pediatricians rarely talk about puberty in terms of a single birthday. Instead, they use the Tanner scale — five stages of physical development that describe where a child actually is in the process, regardless of age. Understanding those stages is one of the most useful things a parent can do, because the growth spurt itself is tied to Tanner stage far more tightly than it's tied to the calendar.
What the Tanner Stages Actually Measure
The Tanner scale was developed by researchers William Marshall and James Tanner, who tracked British children through puberty and published separate reference standards for girls in 1969 and boys in 1970. It sorts pubertal development into five stages, from Stage 1 (childhood, no development) to Stage 5 (physically mature), based on breast development in girls and genital development in boys. A separate pubic hair scale runs alongside it for both sexes.
The key thing the scale is not measuring is height. Tanner stage tracks sexual maturation specifically — the visible result of rising sex hormones. Height growth is driven by the same hormonal surge, which is exactly why the two are so closely linked, but they aren't the same measurement, and a child's stage says nothing about their current height on its own.
Where the Growth Spurt Falls Within the Stages
This is the part most parents actually want to know: at what stage does the big growth spurt happen? A 2015 study following a contemporary US cohort of children found that most girls reach peak height velocity — the single fastest point of the growth spurt — by breast Stage 3, and most boys reach it by genital Stage 4. Specifically, about 69% of girls had already hit their peak by Stage 3, and about 59% of boys had hit theirs by Stage 4.
That word "most" is doing real work in that sentence. The same research also found substantial variability in exactly when peak height velocity lines up with a given stage — enough that the study's authors noted a boy at genital Stage 3 with no growth spurt yet is not necessarily behind, since most boys don't reach their peak until Stage 4. Earlier data collected by Tanner himself, based on a smaller mid-20th-century British sample, had suggested a tighter link between stage and peak velocity than more recent, larger studies actually show.
Girls typically peak earlier in the sequence than boys do. The growth spurt in girls tends to arrive around breast Stage 2–3, well before the later stages of breast maturation are complete. In boys, the spurt tends to arrive later in the sequence, around genital Stage 3–4 — part of why the puberty growth spurt in boys often looks more sudden and dramatic when it finally shows up.
The Five Stages, Side by Side
| Stage | Girls (Breast) | Boys (Genital) | Where the Growth Spurt Usually Stands |
|---|---|---|---|
| Stage 1 | No breast development; prepubertal | Testes, scrotum, and penis are child-sized | Growth spurt has not started. Steady, slow childhood growth continues. |
| Stage 2 | Breast budding begins (thelarche) | Testes and scrotum begin enlarging; scrotal skin changes texture | The spurt is usually just beginning to accelerate from its slowest pre-pubertal point. |
| Stage 3 | Breast and areola continue enlarging, no separate contour yet | Penis begins to lengthen; testes continue enlarging | Most girls have already reached peak height velocity by this stage; boys are still approaching it. |
| Stage 4 | Areola and papilla form a raised secondary mound | Penis increases in width; testes and scrotum larger, scrotal skin darker | Most boys reach peak height velocity by this stage; girls are typically decelerating already. |
| Stage 5 | Mature adult breast contour | Adult genital size and proportion | Growth has slowed substantially for both sexes; final height is approaching as growth plates near closure. |
The Two Age Thresholds That Matter More Than the Stage Itself
How Doctors Use Tanner Staging Alongside Growth Tracking
What This Means For You
The practical takeaway: Tanner stage is a far better predictor of where a child stands in the growth spurt than age alone — most girls have already hit their fastest growth by breast Stage 3, and most boys hit theirs by genital Stage 4, though the exact timing varies more than older textbooks suggest. The two ages that actually matter for a pediatrician are the outer edges: development starting before 8 (girls) or 9 (boys), and no development at all by 13 (girls) or 14 (boys). Everything in between is a wide, normal range. For the mechanics of the spurt itself, see our guide to the puberty growth spurt, and for what "growth is basically done" looks like in practice, see when do boys stop growing and when do girls stop growing.
Frequently Asked Questions
At what Tanner stage does the growth spurt actually happen?
There's no single stage that guarantees it, but research on a contemporary US cohort found that most girls (about 69%) reach peak height velocity by breast Stage 3, and most boys (about 59%) reach it by genital Stage 4. Individual timing varies substantially even within the same stage.
Can I determine my child's Tanner stage myself at home?
It's not recommended as a basis for decisions. Tanner staging is designed to be assessed by a clinician during a physical exam, and self- or parent-assessment is prone to error. A pediatrician can confirm the stage accurately at a routine well-child visit.
My child is at an early stage with no growth spurt yet — is that a problem?
Usually not. Since most children don't reach peak height velocity until breast Stage 3 (girls) or genital Stage 4 (boys), an earlier stage with a growth spurt still ahead is the expected pattern, not a red flag, as long as the child is younger than the delayed-puberty age thresholds.
Do girls and boys go through the same number of stages at the same pace?
Both sexes progress through the same five stages, but girls typically start about two years earlier than boys and tend to reach peak height velocity earlier in the stage sequence. Boys generally take a bit longer to move through the full sequence once it begins.
Does pubic hair development matter as much as breast or genital stage?
It's tracked as a separate scale alongside breast or genital development, and the two don't always progress in perfect sync — pubic hair development is influenced by adrenal hormones (adrenarche), a partly independent process from the ovarian or testicular hormones driving breast or genital maturation. Clinicians generally weight breast or genital stage more heavily when judging overall pubertal timing.
