Tanner stages are a five-point scale that doctors use to track how far along a child or teenager is in puberty. Each stage describes specific physical changes, from no development at all (Stage 1) to full adult maturity (Stage 5). The system looks at two things separately: the growth of breasts or genitalia, and the development of pubic hair. Pediatricians use these stages during routine checkups to make sure puberty is progressing normally and to spot signs that it may be starting too early or too late.
How the Five Stages Work
Stage 1 is simply the prepubescent body, before any visible changes have begun. There’s no breast tissue, no genital enlargement, and no pubic hair. Every child starts here, and the stage itself isn’t really “puberty” at all. It’s the baseline.
Stage 2 marks the true beginning of puberty. For girls, this typically happens between ages 8 and 13 and includes the first signs of breast budding, slight enlargement of the darker skin around the nipple, and a small amount of pubic hair. For boys, Stage 2 usually begins between ages 9 and 14, with the testicles and scrotum starting to enlarge and sparse hair appearing around the genitals.
Stage 3 is when changes pick up speed. Girls see continued breast growth, the start of armpit hair, and thicker pubic hair. Boys notice their penis growing longer, their testicles continuing to enlarge, and pubic hair darkening and coarsening into a triangular pattern. This stage overlaps with the growth spurt for many kids.
Stage 4 represents puberty in full stride. Girls’ breasts take on a more adult shape, and pubic hair becomes thick and curly but stays within a triangular area. For boys, the penis grows in width, the skin of the scrotum darkens, and body hair approaches adult levels. Girls typically reach this stage between ages 10 and 15; boys between 11 and 16.
Stage 5 is full adult maturity. Breast development is complete, genitalia have reached adult size, and pubic hair may spread to the inner thighs. Most people reach Stage 5 by their mid-to-late teens, though the exact timing varies widely.
Tanner Stages in Girls
For girls, doctors evaluate two things independently: breast development and pubic hair. Breast development is often the very first visible sign of puberty, a small mound of tissue beneath the nipple called a “breast bud.” This can feel tender or sore. The area around the nipple gets larger and may darken. By Stage 3, the breasts become rounder as the milk-producing glands and fatty tissue grow, and the nipples start to protrude more. By Stage 4 and 5, the breast reaches its adult size and contour.
Pubic hair follows its own timeline. It begins as a few fine hairs along the labia in Stage 2, gradually becomes coarser and darker, fills in a triangular pattern by Stage 4, and may extend slightly beyond that triangle in Stage 5. Because breast and pubic hair development don’t always move in lockstep, a girl could be Stage 3 for breast development but Stage 2 for pubic hair. That’s normal.
The first period typically arrives around Stage 3 or 4, usually about two to three years after breast budding begins.
Tanner Stages in Boys
For boys, the scale tracks genital development and pubic hair separately. The earliest sign of puberty is almost always testicular enlargement, not the more obvious changes like voice deepening or facial hair. In Stage 2, the testicles begin to grow and the scrotal skin changes in color and texture, while the penis itself shows little or no change yet. By Stage 3, the penis starts growing in length and the testicles continue to enlarge. Stage 4 brings growth in penis width, development of the glans (the tip), and scrotal skin that darkens further. Stage 5 is full adult size.
Pubic hair in boys follows a familiar arc: sparse and fine in Stage 2, darker and triangular by Stage 3, dense and curly by Stage 4, and potentially spreading to the inner thighs by Stage 5. Body and facial hair, voice changes, and significant muscle development tend to come later, generally in Stages 3 through 5.
Normal Age Ranges
There’s a wide window for what counts as normal. Girls typically enter Stage 2 somewhere between ages 8 and 13. Boys usually begin between 9 and 14. The entire process from Stage 2 to Stage 5 takes roughly three to five years, though some kids move through faster or slower.
Genetics play the biggest role in timing, but nutrition, body weight, and environmental factors also matter. There’s solid evidence of a global trend toward earlier puberty onset in girls over the past several decades, meaning the average age of breast budding has shifted slightly younger compared to previous generations. Whether this shift has meaningfully changed the upper end of normal (when it’s considered “late”) is still unclear.
Why Doctors Use Them
Tanner staging gives pediatricians a shared language to describe where a child is in development. During a physical exam, the doctor visually assesses breast or genital development and pubic hair, then assigns a stage number for each. For boys, they may also measure testicular volume using a string of graduated beads called an orchidometer. At the start of puberty (Stage 2), median testicular volume is about 4 to 5 milliliters; by Stage 5, it reaches around 20 milliliters.
These assessments help identify two main concerns. Precocious puberty is when Stage 2 changes appear before age 8 in girls or age 9 in boys. Delayed puberty is when there are no signs of development by age 13 in girls or age 14 in boys. Both situations can be evaluated further, and in many cases they turn out to be normal variations. But they can also signal hormonal conditions that benefit from early treatment, which is why routine tracking matters.
Tanner stages also come up in sports medicine, growth hormone evaluations, and orthopedic decisions (like timing surgery around a growth spurt). If your child’s doctor mentions a Tanner stage during a visit, it’s simply a shorthand for how far along puberty has progressed, not a judgment about whether your child is developing “correctly.” The range of normal is broad, and two kids the same age can easily be two or three stages apart.