Guys typically stop growing in height around the age of 18 when their growth plates (epiphyseal plates) fuse, marking the end of vertical bone growth. However, some men may experience small growth spurts until their early 20s, but significant growth after 21 is very rare. Growth generally stops once the cartilage in the growth plates hardens into bone, which prevents further lengthening of bones. This age range can vary depending on genetics, health during childhood, and hormonal factors. Boys who begin puberty later may continue growing slightly later as well. After the age of about 25, growth in height is essentially complete, though men may still increase muscle mass and change in other physical ways. In summary:
- Most guys stop growing by 18
- Some may grow a little until early 20s (rarely beyond 21)
- Growth plates fusion is the biological marker for ending height increase
- Full physical maturity is usually reached by 18-25 years depending on the individual.
