When Do Boys Stop Growing? Height Timeline & Factors

If you’ve ever wondered whether that lanky 14-year-old still has a few more inches left in him, you’re not alone — it’s one of the most common questions parents and teens ask their doctors. The short answer is that most boys finish growing taller sometime between 16 and 18, with complete growth plate closure for virtually all males by age 21. What actually determines that finish line? Growth plates — strips of cartilage at the ends of long bones that produce new tissue during puberty and eventually seal shut, locking in final adult height.

Typical stop age for height growth: 16-18 years · Peak growth spurt age: 13-15 years · Average male final height: 5’9″ (175 cm) · Growth plates close by: age 18 for most

Five key stages span male growth, each driven by a different biological trigger.

These milestones show how growth plate fusion progresses from onset to completion, with the final stage representing when all sites seal shut.

Do boys grow after 18?

Technically, yes — but only if growth plates remain open. That’s the biological gatekeeper. A 2021 study published in PMC found that 50% of boys have fused growth plates between 15 and 18 years, while 90% have fused by 17 to 20. Complete closure at all sites occurs by age 21 (PMC Study (PubMed Central)). Once that cartilage turns to bone, height growth stops — full stop.

“Males can keep growing as long as their growth plates haven’t closed, which usually happens by age 18,” said Joshua Coleman, MD, a pediatrician at Cleveland Clinic. For late bloomers — boys whose constitutional delayed puberty pushes the entire timeline back — growth can continue into the early twenties. The trade-off is that these boys often catch up later rather than earlier, reaching their adult height around 18 instead of 16 (Cleveland Clinic). A growth spurt is very unlikely after 18, and there’s no credible evidence showing men continue growing past 25.

Late bloomer cases

Boys who start puberty after 13 often experience a delayed but complete growth trajectory. They may be shorter than peers in high school, then suddenly sprout in their late teens. Dr. Coleman notes that constitutional delayed puberty doesn’t prevent boys from reaching their genetically predetermined adult height — it just takes longer. These late bloomers can gain an extra 3-4 inches after age 16 before their plates finally close.

Do boys stop growing at 16 or 21?

Six years apart, but both can be true. Most boys stop growing between 16 and 18 years old. Boys who start puberty earlier — say, at 10 instead of 12 — tend to finish earlier too, sometimes by 16. Boys who start later may not finish until 19 or even 20. Complete closure at all sites happens by 21 for virtually every male, according to research in PMC (PMC Study (PubMed Central)). Growth beyond 21 is biologically implausible without pathological causes like acromegaly.

The most reliable way to assess whether a boy still has growth potential is an X-ray of the hand and wrist. Radiologists can read growth plate status against standardized atlases and give a bone age estimate. “X-rays are most reliable to assess growth plate closure,” according to Vinmec International Health Hub (Vinmec). This is the standard clinical method when height prediction matters — think sports physicals or pediatric endocrinology consultations.

When do boys stop growing: Height, genitals, and what to expect

Height is only one part of male pubertal development. The entire package — genital maturation, muscle growth, facial hair, voice deepening — typically concludes by 16 to 18 years old, matching the height growth timeline.

Height specifics

Growth plates close near the end of puberty: girls 13-15 years, boys 15-17 years, according to Nemours KidsHealth (Nemours KidsHealth). Most boys reach adult height by 16-18 years old, though some add a few more inches into their late teens. The average adult male height in the United States is 5’9″ (175 cm) based on CDC population data.

Other changes

Boys also experience shoulder widening, increased muscle mass from testosterone, facial hair growth, voice deepening, and acne during puberty. Foot size grows alongside height — foot bones stop developing around the same time as long bones, typically between 16-19 years old (Cleveland Clinic). This is why shoe shopping becomes unpredictable during the teen years.

Will boys grow after age 16?

Many will. Boys who hit puberty at the average age of 12 typically experience their fastest growth between 13 and 15, then slow down and stop around 16-17. But those who started later may still be in active growth phase at 16 — and could add 1-2 more inches before plates close. A 2021 PMC study found that 50% of boys have fused growth plates by age 16-18, which means the other half still have open plates at that point.

Signs of ongoing growth include a recent growth spurt, increasing shoe size, deepening voice, and body hair development. Boys who haven’t experienced their voice breaking or acne onset by 16 may still be in active puberty. The only clinical way to know for certain is an X-ray — anything else is an estimate.

The implication is that timing matters more than age — a 16-year-old who started late still has runway, while one who started early may be done.

How tall will a boy grow after 16?

Prediction methods exist, but they’re imprecise. The mid-parental height calculator is the most widely used tool: take the midpoint of both parents’ heights, then add 2.5 inches for boys. This gives a target range within ±2.5 inches.

Genetics accounts for roughly 80% of final height, with nutrition, overall health, and medical conditions filling in the rest. Poor nutrition during growth years can prevent a boy from reaching his genetic potential — not by a little, but by 1-4 inches in severe cases. Chronic conditions like inflammatory bowel disease, kidney disease, or hormonal disorders can also blunt growth. Boys who started puberty before age 9 (early puberty) tend to be shorter as adults because their growth plates close earlier than peers.

Males can keep growing as long as their growth plates haven’t closed, which usually happens by age 18. A growth spurt is very unlikely to happen past age 18.

— Joshua Coleman, MD, Pediatrician, Cleveland Clinic (Cleveland Clinic)

Most children stop growing about 2 years after the end of puberty, typically ending at 14 years old for girls and 16-17 years old for boys.

— Andre C. Grant, MD, Orthopedic Surgeon at Duke Orthopedics (Vinmec)

For parents watching a teenage boy compare himself to teammates or classmates, the key variable is puberty start date — not age on a calendar. A 16-year-old who started late still has runway left. A 16-year-old who started at 10 may be done. For those boys still growing into their late teens, there’s good news: they’ll get there, just on their own schedule.

Related reading: Muscles of the Body · 160cm in Feet and Inches

Boys usually stop growing in height by ages 16 to 18, influenced by puberty and genetics as this age timeline and factors thoroughly outlines.

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