Growth spurts last anywhere from a few days to several years, depending on age. In infants, a single growth spurt typically wraps up within two to three days. In adolescents, the major pubertal growth spurt stretches over roughly four to five years, with a shorter peak phase inside that window when height increases most dramatically.
Infant Growth Spurts: Days, Not Weeks
Babies experience several brief growth spurts during their first year, each lasting up to about three days. These episodes tend to hit quickly and feel intense for parents, but they pass fast. The most common timing for infant growth spurts is around 2 to 3 weeks, 6 weeks, 3 months, 6 months, and 9 months of age.
During these short bursts, babies often seem hungrier than usual and may want to feed more frequently, sometimes cluster-feeding for hours. They can also be fussier and sleep more, or sleep less restfully. These behavioral changes are often the only way parents notice a spurt is happening, since you’re unlikely to see a visible height change in just a couple of days. If your baby suddenly seems insatiable and clingy for a day or two and then returns to normal, a growth spurt is the most likely explanation.
The Adolescent Growth Spurt
The pubertal growth spurt is a different animal entirely. It begins around age 10 in girls and 12 in boys and lasts until roughly 14.8 and 17.1 years, respectively. That’s close to five years of accelerated growth for both sexes, even though the duration doesn’t differ much between boys and girls.
Before puberty, children grow at a steady pace of about 5 centimeters (2 inches) per year. During the peak of the pubertal spurt, girls reach about 8.3 cm/year (just over 3 inches) and boys hit roughly 9.5 cm/year (close to 4 inches). Boys also gain weight rapidly during this phase, going from about 3 kg/year before puberty to around 9 kg/year, with most of that gain coming from muscle and lean tissue rather than fat.
This peak velocity phase, the fastest stretch within the larger spurt, typically lasts one to two years. The years on either side of the peak involve noticeable but slower acceleration. So while the entire spurt spans four to five years, the phase where growth feels most dramatic is considerably shorter.
When Growth Stops Completely
Height increases end when your growth plates, the strips of cartilage near the ends of long bones, fuse into solid bone. This follows a predictable pattern: the heel fuses first, then the shin and thigh bones, and finally the wrist. Girls complete this process about two years earlier than boys. By age 17, roughly 75 to 98 percent of girls have fused growth plates at all major sites. For boys, the same milestones occur around age 19. All girls in one large MRI study had fully closed plates by 19, while all boys were closed by 21.
This means that even after the main growth spurt winds down, a small amount of height can still be added in the final year or two before full closure. Some teens who feel like they’ve “stopped growing” at 15 or 16 may still gain another centimeter or two before the plates seal.
Why Sleep Matters So Much During Growth
The body’s growth hormone is released in pulses throughout the day, but the largest and most consistent pulse happens shortly after you fall asleep, during the deepest phase of sleep. In men, about 70 percent of growth hormone pulses during sleep coincide with this deep sleep stage, and the amount of hormone released directly correlates with how much deep sleep occurs. This relationship holds from early childhood through adulthood.
For children and teens in an active growth spurt, consistently poor or shortened sleep can blunt these hormone pulses. This is one reason growing children and adolescents naturally tend to sleep longer, and why protecting sleep quality during the pubertal years is more than just good hygiene.
Nutritional Needs During a Growth Spurt
Calorie requirements jump significantly during puberty. Girls ages 9 to 13 generally need 1,400 to 2,200 calories per day, rising to 1,800 to 2,400 for ages 14 to 18. Boys need more because of their larger frames and greater muscle mass: 1,600 to 2,600 calories for ages 9 to 13, and 2,000 to 3,200 for ages 14 to 18. The wide ranges reflect differences in activity level and body size.
Beyond calories, the body needs more iron, calcium, zinc, and folate during rapid growth. Interestingly, protein needs during puberty don’t actually increase much when adjusted for body weight. The same relative intake that works before puberty appears sufficient to support the muscle and tissue building that accelerates during the spurt.
Growing Pains: What They Feel Like
Between 25 and 40 percent of children experience what doctors call “growing pains,” though the name is somewhat misleading since the pain hasn’t been definitively linked to the physical process of growing. The episodes typically involve an aching feeling in both legs, most often in the calves, front of the thighs, shins, or behind the knees. About 80 to 90 percent of children with growing pains report the discomfort on both sides.
The pain tends to show up in the early evening or at night, and it often wakes children from sleep. Individual episodes last minutes to hours, and the key distinguishing feature is that the pain is completely gone by morning. Children can go days or weeks between episodes with no discomfort at all. The pain is not related to physical activity during the day. If your child’s leg pain is consistently one-sided, still present in the morning, or accompanied by swelling, redness, or limping, those are signs of something other than growing pains worth getting evaluated.