Most girls reach their full adult height around age 14 to 16, while most boys stop growing between 16 and 18. The exact age depends on when you enter puberty, your genetics, and how quickly your growth plates close. In rare cases, some boys continue to grow into their early twenties, though usually by no more than an inch.
Why Girls and Boys Stop Growing at Different Ages
Girls typically hit their peak growth spurt earlier in puberty, around ages 10 to 14, and reach their final height about one to two years after their first period. After that first period, most girls grow an average of 2 to 3 inches before height gain stops entirely. Since girls generally start puberty earlier than boys, they also finish growing earlier.
Boys tend to begin their growth spurt later, usually between ages 12 and 16, and keep gaining height until roughly 16 to 18. The later start gives boys more years of gradual pre-puberty growth, which is one reason males end up taller on average. A small number of boys add a little height past 18, but this is uncommon. CDC growth charts track children up to age 20, and for the vast majority of people, the height curve has completely flattened well before that point.
What Actually Stops Your Bones From Growing
Height comes from the lengthening of long bones in your legs and spine. Near each end of these bones, there’s a strip of cartilage called a growth plate. Throughout childhood and adolescence, cells in this cartilage multiply, pushing the bone longer. New bone tissue then replaces the older cartilage closer to the center of the bone. As long as this cycle continues, you keep getting taller.
Estrogen is the hormone that ultimately shuts this process down, and it plays this role in both males and females. As puberty progresses and estrogen levels rise, the cartilage cells in the growth plate lose their ability to keep dividing. Estrogen doesn’t directly turn cartilage into bone. Instead, it speeds up the natural aging of those cartilage cells, exhausting their capacity to reproduce. Once the cells stop dividing entirely, the remaining cartilage is quickly replaced by solid bone. At that point, the growth plate fuses into a thin line, and the bone can no longer lengthen. This fusion typically happens by the early twenties at the latest, though for most people it occurs several years sooner.
This is why children who enter puberty very early tend to be tall for their age initially but may end up shorter as adults. The early rise in estrogen fuses their growth plates sooner, cutting short the total window for growth.
Late Bloomers and Constitutional Growth Delay
Some teenagers are noticeably shorter than their peers through middle and high school but eventually catch up. This pattern, called constitutional growth delay, is especially common in boys with a family history of late puberty. Their bone maturation often lags behind their actual age by two years or more, which means their growth plates stay open longer. They start puberty later, continue growing after most of their classmates have stopped, and typically reach a normal adult height for their family.
If you’re 16 or 17 and feel like you haven’t grown much while everyone around you has, a bone age X-ray can show whether your growth plates are still open and how much growth potential remains. A bone age that’s significantly younger than your calendar age is a strong sign that more height is coming.
Can You Grow Taller After 20?
For the vast majority of people, the answer is no. Once growth plates have fully fused, no exercise, supplement, or diet will restart bone lengthening. Some products marketed as height boosters claim to reopen growth plates or stimulate growth hormone, but there is no evidence that any of them work once fusion is complete.
There is one rare medical condition worth knowing about. When the pituitary gland produces excess growth hormone before puberty, it causes a condition called gigantism, which leads to unusually tall stature. When the same overproduction happens after puberty, it’s called acromegaly. Because growth plates are already closed in adults with acromegaly, it does not increase height. Instead, it causes the bones of the hands, feet, and face to thicken and enlarge. Acromegaly is uncommon and produces other noticeable symptoms well beyond any changes in bone size.
Why Your Height Changes During the Day
Even after you’ve stopped growing, you may notice that you measure slightly taller in the morning than at night. This isn’t actual growth. The discs between the vertebrae in your spine are filled with fluid and act like small cushions. Overnight, while you’re lying down, they absorb water and expand slightly. Throughout the day, gravity compresses them again. Research from the University of Southampton found that people lose about a third of a centimeter in height between 9 a.m. and 11 a.m. alone, with most of the shrinkage happening by early afternoon. This means your “true” height depends partly on when you measure it. If you want a consistent number, measure at the same time of day.
Factors That Influence Your Final Height
Genetics is the dominant factor, accounting for roughly 60 to 80 percent of your adult height. If both of your parents are tall, you’re likely to be tall. If one parent was a late bloomer, you may follow a similar timeline. But genetics sets a range, not a fixed number, and several other factors determine where you land within that range.
- Nutrition: Consistent access to protein, calcium, vitamin D, and overall adequate calories during childhood and adolescence supports full growth potential. Chronic malnutrition during key growth periods can result in shorter adult height.
- Sleep: Growth hormone is released primarily during deep sleep. Consistently poor sleep during puberty can reduce the amount of growth hormone available during the years when it matters most.
- Chronic illness: Conditions that affect nutrient absorption, hormone levels, or overall health during childhood, such as celiac disease, thyroid disorders, or growth hormone deficiency, can slow or limit height gain if untreated.
- Physical activity: Regular exercise supports healthy bone development, though no specific sport or exercise will make you taller than your genetic potential allows.
The window for influencing these factors is during childhood and adolescence, while growth plates are still active. Once they close, the opportunity to affect final height has passed.