For most girls, the growth spurt begins between ages 10 and 12 and peaks around 11 to 12. For most boys, it starts about two years later, typically between ages 12 and 15. But these windows vary widely from person to person, and the physical signs of puberty are a more reliable guide than age alone.
Growth Spurt Timing for Girls
Girls generally hit their fastest rate of growth earlier than boys. The spurt often kicks off shortly before or around the time breast development begins, which can happen as early as age 7 in some healthy girls. At its peak, girls grow an average of about 8.3 centimeters (roughly 3.3 inches) per year.
One of the most useful landmarks for girls is their first period. After menarche, girls typically gain about 7 centimeters (3 inches) of additional height, though the exact amount depends on how early or late that period arrives. Data from the Fels Longitudinal Study shows that girls who start menstruating at age 10 grow about 10 centimeters (4 inches) afterward, while those who don’t get their period until age 15 tend to grow only about 5 centimeters (2 inches) more. So an earlier period doesn’t necessarily mean a shorter final height, because those girls often had more growing time before it arrived.
Growth Spurt Timing for Boys
Boys tend to start their growth spurt about two years after girls, which is why many 12-year-old boys find themselves temporarily shorter than their female classmates. The fastest growth usually happens between ages 12 and 15, with peak height velocity averaging about 9.5 centimeters (3.7 inches) per year. Most boys continue growing until around age 16, though some add small amounts of height into their late teens.
The pubertal growth spurt in boys typically begins about six months after the first visible signs of puberty, such as testicular enlargement. Because boys start later but grow at a faster peak rate and for a longer overall period, they end up, on average, taller than girls by the time growth is complete.
Physical Signs That Predict the Spurt
Calendar age gives you a rough estimate, but the physical changes of puberty are a better predictor of where someone is in their growth spurt. Doctors use stages of development (breast stages for girls, genital stages for boys) to track this.
For girls, the middle of the growth spurt lines up closely with the transition from early to moderate breast development. About 70% of girls have completed half their pubertal height gain by that stage. For boys, the midpoint of the spurt tends to fall during moderate genital development, with roughly 74% of boys reaching the halfway mark of their pubertal growth around that stage. In practical terms: if a boy has only just started showing the earliest signs of puberty, most of the growth spurt is still ahead. If a girl already has noticeable breast development, she’s likely in the thick of it or past the peak.
What Drives the Spurt
The growth spurt isn’t just “more growing.” It’s a distinct hormonal event. During puberty, the body ramps up production of growth hormone dramatically, with levels increasing 1.5 to 3 times compared to childhood. At the same time, a key growth-signaling molecule called IGF-1 surges more than threefold. These two signals together drive rapid bone lengthening.
Estrogen plays a central and somewhat surprising role in both sexes. It’s the primary hormone that accelerates growth plate activity (the zones at the ends of bones where new bone forms) during the spurt. But estrogen also eventually causes those growth plates to fuse and close permanently, which is what stops growth altogether. Testosterone contributes by amplifying growth hormone output. This is part of why boys, who produce more testosterone for a longer period before estrogen levels rise enough to close growth plates, tend to grow taller overall.
Early and Late Bloomers
There’s a wide range of normal. Some kids show the first signs of puberty at 8 or 9, others not until 13 or 14. Both can be perfectly healthy. The clinical thresholds for concern are specific: doctors consider puberty delayed if a girl shows no breast development by age 13, or if a boy shows no testicular enlargement by age 14. On the other end, puberty before age 7 in girls or before age 9 in boys may warrant evaluation.
Late bloomers often worry about falling behind their peers in height. This is common and usually temporary. These kids typically cross down to a lower height percentile on growth charts during the years when their peers are spurting, then catch up once their own spurt begins. If puberty has started but takes longer than five years to complete, or if a girl hasn’t had her first period by age 15, that’s when further evaluation becomes relevant.
Nutrition During the Growth Spurt
Bones are growing faster during the pubertal spurt than at any time since infancy, and they need the raw materials to do it. Three nutrients matter most during this window: calcium, vitamin D, and zinc.
- Calcium: Teens aged 14 to 18 need 1,300 milligrams per day, which is higher than the adult requirement. That’s roughly the equivalent of four glasses of milk, though dairy isn’t the only source. Fortified foods, leafy greens, and canned fish with bones all contribute.
- Vitamin D: The recommended intake is 600 IU per day for teens, though some researchers suggest 600 to 1,000 IU may be more appropriate. Vitamin D is essential for calcium absorption, so getting enough calcium without adequate vitamin D doesn’t do much good.
- Zinc: Boys need about 11 milligrams per day and girls about 9 milligrams. Zinc supports both bone growth and the hormonal signaling that drives puberty. Meat, shellfish, legumes, and seeds are good sources.
Adequate protein and overall calorie intake also matter. Chronic undernutrition can delay puberty and blunt the growth spurt. This doesn’t mean eating more will make someone taller than their genetics allow, but consistently falling short on key nutrients during these years can prevent someone from reaching their full potential height.