When Do Boys Stop Growing?

The age when boys stop growing has a lot to do with when they start puberty and whether or not they're a "late bloomer." Experts explain what to expect, plus a few common height prediction methods doctors use.

The age boys stop growing varies, but typically, it is around their 18th birthday. Children grow at different rates but there are some typical patterns that most kids follow. It's common knowledge that boys don't mature physically at the same pace as girls, but that growing gap isn't as wide before age 10.

Learn more about how boys grow in height and when they typically reach their final height. Additionally, we share three common height prediction methods used by pediatricians.

While this article uses the terms "boy" and "girl," it's important to note that gender is a personal identity that exists on a spectrum, can change over the course of a person's lifetime—and most importantly—is something that a person defines for themselves. Sex, on the other hand, is assigned at birth based on the appearance of a baby's genitalia. While sex assigned at birth often matches a person's gender (called cisgender), sometimes, for transgender, intersex, and gender nonbinary people, it does not.

When Do Children Have Growth Spurts?

"Growth spurts aren't common in the 3-10 age range," explains Zoltan Antal, M.D., chief of pediatric endocrinology at New York-Presbyterian Komansky Children's Hospital and Weil Cornell Medicine. "Most prepubescent children grow 2 inches or 5 centimeters a year on average."

Girls do most of their growing at the start of puberty, which can be as early as age 8 for them, and reach their final adult height around two years after their first period. Boys experience peak acceleration of growth much later, usually between ages 13 to 15, since they typically enter pubertal development around age 12 (though some "early bloomers" may start puberty at 9 or 10, says Dr. Antal). Some boys may start puberty a year or two later than average, as well.

When Do Boys Stop Growing in Height?

The age at which children stop growing in height depends on their sex and other factors. Although male children get a later start compared to their female peers, they eventually catch up, and then some. Most girls stop growing taller by age 14 or 15. However, after their early teenage growth spurt, boys continue gaining height at a gradual pace until around 18.

Note that some kids will stop growing earlier and others may keep growing a year or two more. This variation is normal, but the average boy will stop growing around age 18. Essentially, when puberty stops, so does most of their growth.

Height Prediction Methods for Boys

While there's no 100% accurate way to determine how tall children will become in adulthood, there are three methods pediatricians commonly employ to predict adult height for both boys and girls. Research shows that while these methods (as well as others that have been developed) often produce valid estimates, they also have a wide range of deviation. This means that the estimate you end up with is a possible height range spanning several inches rather than an exact expected height.

Factors that impact accuracy

Future adult height estimates tend to be more accurate for healthy children in the middle height range. These tools may be slightly less accurate for shorter or taller children. Additionally, notes the American Academy of Pediatrics (AAP), nutritional, medical, hormonal, or genetic issues may impact future adult height. For example, some medications, such as corticosteroids, and chronic illnesses like cancer or celiac disease can slow growth.

Your child's pediatrician can offer a more accurate height prediction as they will take all these factors into account when estimating your child's future height.

Mid-parental height calculator

Many doctors use what's known as a "mid-parental height calculator" to determine a range of how tall boys will grow to be, says Danton Kono, M.D., a pediatrician with Dignity Health Mercy Medical Group in California, though he's quick to add that the method is "still very inaccurate."

To get the estimated range, you take the boy's biological mother's height and add 5 inches, then average that number with the boy's biological father's height. The resulting height, plus or minus 3.35 inches, is how tall you can expect the boy to become. For instance, if their dad is 5'10" and their mom is 5'2", you would add 5'10" to 5'7" and divide that sum by two to get 5'8½"—their son should grow to be 5'8½", give or take a few inches.

Two times two method

The AAP also recommends the "two times two" method. This simple approach starts with the toddler's height at age 2, then doubles it for a future adult height measurement. So, if your son is 2'11" at age 2, their predicted height as an adult is 5'10". The AAP notes, "While this method has been around for a long time, no research exists to demonstrate its accuracy." However, it's an easy way to get a good rough estimate.

Following the growth chart curve

Dr. Antal prefers another method. "For a child who's going through puberty, you find their height percentile on a growth chart, and follow the corresponding curve out," he explains. For example, if you look at the Centers for Disease Control and Prevention (CDC) growth chart for boys 2 to 20 years, a 13-year-old boy who is 5'1" (61 inches tall) is in the 50th percentile. Based on that curve, he should reach an adult height between 5'9" or 5'10" (69-70 inches).

The CDC growth chart also shows weight-for-age percentiles that allow parents to estimate what their son might weigh in the future. Using the same example of the 50th percentile, a 13-year-old boy who weighs just over 100 lbs can expect to weigh roughly 155 by the time they're an adult if they continue developing at an average pace.

When to See a Doctor

If it seems like every other kid is growing but not your own, don't worry just yet. "Children with delayed growth, what's known as constitutional growth delay, experience slow and steady growth," says Dr. Kono. "In this scenario, even though a boy may not be maturing very fast, he's still going to be a normal adult height."

However, if you have converns about your child's growth, their pediatrician can do a bone age X-ray in the office to determine if your child's growth is on track. "If I get an X-ray of a 14-year-old boy and his bones look like those of a 12-year-old, that tells me he's still got five or six years of growth left and he won't achieve his final adult height until maybe even college age," says Dr. Kono.

However, if your son is falling off of the growth curve and not catching up with their peers, there could be something medically wrong, like a growth hormone deficiency, adds Dr. Kono.

"It's important to ask your pediatrician about where the child is in puberty and whether they are growing appropriately for their stage of puberty," says Dr. Antal. If you wait until your son is almost finished with puberty, there's not much an endocrinologist, a type of physician who specializes in conditions relating to hormones, can do to help.

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