Most boys stop growing in height between ages 16 and 18, with the majority reaching their final adult height by 18. Some continue to grow slightly into their early 20s, but this is uncommon. The timeline depends largely on when puberty started, how quickly it progresses, and genetics.
The Male Growth Timeline
Boys follow a fairly predictable pattern of growth from childhood through the end of puberty. Before puberty begins, most boys grow about 2 inches per year. Once puberty kicks in, usually between ages 9 and 14, that pace starts to accelerate.
The peak growth spurt for boys happens around age 13.7 on average, when they can gain roughly 4.4 inches (11.3 cm) in a single year. That’s noticeably faster than the female peak, which occurs earlier and tops out at about 3.9 inches per year. After this peak, growth gradually slows. By age 16, an average boy has already reached about 98% of his adult height. CDC growth charts show that the 50th percentile male measures about 173.4 cm (5’8″) at 16 and reaches 176.5 cm (5’9.5″) by 20, gaining just over an inch across those final years.
Growth doesn’t stop abruptly. It tapers. A boy might gain 2 inches between 14 and 15, then an inch between 15 and 16, then half an inch between 16 and 17, then barely anything after that.
Why Growth Eventually Stops
Height growth happens at the growth plates, which are bands of cartilage near the ends of long bones in the legs and spine. During childhood and puberty, these plates produce new bone tissue, making the bones longer. Once the plates harden and fuse into solid bone, no more lengthening is possible.
The hormone that ultimately triggers this fusion is estrogen. While estrogen is often associated with females, males produce it too, primarily by converting testosterone. As testosterone levels rise throughout puberty, estrogen gradually accumulates. At low levels, estrogen actually stimulates growth. But as levels climb higher, it slows the cartilage cells in the growth plates and eventually signals them to close permanently. This process happens later in males than in females because estrogen rises more slowly in boys, which is one reason men end up taller on average.
Growth plate fusion typically completes by age 17 to 18 in most males. Once the plates are closed, no supplement, exercise, or diet can add more height.
Physical Signs That Growth Is Finishing
Because height growth and puberty are linked, the physical changes of late puberty are reliable signals that a boy is nearing his final height. The last stage of puberty brings adult-level facial hair, a fully deepened voice, full development of the chest and shoulders, and adult muscle mass. If a boy has reached this stage, sometimes called stage 5 of pubertal development, he has little to no height left to gain.
Boys who still have visible signs of ongoing puberty, like a voice that’s still cracking, sparse facial hair, or continued broadening of the shoulders, likely still have some growth ahead. Those who look physically mature and haven’t grown in 6 to 12 months have almost certainly finished.
Late Bloomers and Early Developers
Not every boy follows the average timeline. “Late bloomers” are boys whose puberty starts significantly later than their peers, typically after age 14. The medical term is constitutional delay of growth and puberty, and it’s the most common reason a teenage boy appears much shorter than his classmates. These boys often have a family history of late development, with a father or mother who also hit puberty late.
The reassuring part is that late bloomers usually catch up. Because their growth plates stay open longer, they continue growing after their peers have stopped. A boy who starts puberty at 15 might not finish growing until 20 or 21. His final height is typically normal for his family, just delayed. On the flip side, boys who enter puberty early (around age 9 or 10) may hit their growth spurt sooner but also stop growing sooner, sometimes finishing by 14 or 15.
Estimating Adult Height
If you’re wondering how tall a boy will eventually be, the simplest tool is the mid-parental height formula recommended by the American Academy of Pediatrics. For boys, you add the mother’s height plus 5 inches to the father’s height, then divide by two. The result is the predicted adult height, with a range of plus or minus 4 inches covering 95% of outcomes.
For example, if a boy’s mother is 5’4″ and his father is 5’10”, the calculation would be: (69 inches + 70 inches) / 2 = 69.5 inches, or about 5’9.5″. That boy would be expected to reach somewhere between 5’5.5″ and 6’1.5″. The range is wide, which reflects how many genes contribute to height and how much variation exists even within families.
A more precise method involves a bone age X-ray, which shows how mature the growth plates are compared to the child’s actual age. If a 14-year-old has a bone age of 12, he has significantly more growth ahead than his age alone would suggest.
What Actually Affects Final Height
Genetics account for roughly 60 to 80% of a person’s final height. The remaining portion comes from environmental factors, and most of these matter long before a boy is old enough to Google his height potential.
Nutrition during childhood and puberty plays a real role. Chronic malnutrition or severe calorie restriction during growth years can limit final height. Adequate protein, calcium, vitamin D, and zinc support normal bone growth, though no specific food or supplement will push a boy beyond his genetic ceiling. Sleep also matters because growth hormone is released primarily during deep sleep. Teenagers who consistently get fewer than 7 to 8 hours may not optimize their growth, though the effect is modest in well-nourished populations.
Exercise supports overall health and bone density but doesn’t meaningfully increase or decrease final height. The old concern that weightlifting stunts growth in teenagers has not been supported by evidence, as long as the exercises are performed with proper form and age-appropriate loads.