At age 16, you can drive a car. At 18, you’re legally an adult in most states. At 21, you can legally buy alcohol. But at what age do you stop growing taller?

Even if you hit puberty late, you’re unlikely to grow significantly after the ages of 18 to 20. Most boys reach their peak height around the age of 16. However, men still develop in other ways well into their twenties.

Research has found that the brain doesn’t fully develop until the age of 25 and men usually achieve peak muscle mass somewhere between the age of 20 and 30.

In this article, we’re going to discuss when guys typically stop growing and factors that determine how tall you’ll be.

Boys grow fastest during puberty. Some boys may begin puberty as early as nine while others might not hit it until they’re 15. For many guys, their biggest growth spurt will be between the ages of 12 to 15.

Puberty can last two to five years. Spending more time in puberty doesn’t mean that you’ll be taller than somebody who spends less time in it.

Growth charts show that majority of guys grow just a little after the ages of 18. In rare cases, some people may hit puberty in their late teens and continue to grow into their early twenties.

The reason most guys stop growing at this age is because their growth plates fuse shortly after puberty. Growth plates are layers of cartilage found near either end of long bones of children and adolescents. They’re the part of the bone that grows longer.

Once a bone is fused, it can’t continue to grow longer.

Your height is largely determined by your genetics. External factors like the amount of sleep you get and your nutrition also play a role in determining how tall you’ll grow.

Genetics

Genetics play the largest role in determining how tall you’ll be. It’s estimated that about 80 percent of your height is determined by your genetics. The other 20 percent is influenced by external factors.

You can estimate a child’s height by using the mid-parental method:

  1. Add the heights of the child’s mother and father together and divide by two.
  2. If the child is a boy, add 2.5 inches. If the child is a girl, subtract 2.5 inches.

For example, if a male child’s dad is 5’11” and mom is 5’4,” the child will likely be around 5’10.” However, this is just a rough guide, not an exact prediction.

Nutrition

Besides your genetics, nutrition has the biggest influence on your height. Children who don’t get enough of one or more essential nutrients often experience stunted growth.

Protein deficiency is the common nutrient deficiency that limits height. Mineral, vitamin D, and vitamin A deficiencies also impact growth.

Sleep

Your body produces growth hormone and thyroid-stimulating hormone when you’re sleeping. Both these hormones are essential for the proper development of bones.

Not getting adequate sleep is thought to stunt growth, although more research is needed to fully understand the role of sleep on height development.

Medications

Some stimulant medications used to treat attention deficit disorder may cause delays in growth. However, more research is needed to understand their effects.

A 2015 observational study looked at the link between central stimulants to treat ADHD and stunted growth. The study assessed 410 children between the age of 0.9 to 16.1. The researchers found that the medication led to a temporary halt in both increases in height and weight. Even after taking medication for six years, the children still hadn’t caught up to their predicted growths.

Another study published in 2014 followed a cohort of 340 kids with ADHD into adulthood. They concluded that stimulant medication didn’t affect the children’s height in adulthood.

Health conditions

Various genetic or chronic conditions can lead to stunted growth. Some conditions include:

Average height of men in the United States

According to the Centers for Disease Control and Prevention, the average height of men in the United States is about 5 foot 9 inches. Source data was collected from 1999 through 2016.

Healthline

There’s little you can do to influence your height once your growth plates fuse. Even regular exercise and a healthy diet are unlikely to influence your height.

You may be able to make a small gain in height by improving your posture. Improving your posture will help straighten your spine but won’t make your bones grow longer.

Some ways you may be able to improve your posture include:

  • regular stretching
  • strengthening your core
  • sitting with good posture regularly
  • exercising regularly
  • avoiding slouching

Your height fluctuates by roughly 0.3 inches from the time you wake up to the time you go to bed due to compression on your spine throughout the day. If you measure yourself in the morning, you’ll likely notice that you’re slightly taller than you are in the evening.

If you’re still growing, eating a balanced diet and getting plenty of sleep can help you maximize your genetic potential for growth.

It’s important for children to get regular checkups with a pediatrician so they can have their growth tracked over time. Their doctor can compare their growth curve those of other children their age to see if they’re progressing normally.

A doctor can also answer any specific concerns you may have about your or your child’s height.

Your genetics are the biggest factor that determine how tall you’ll be.

External factors like your diet and the amount of sleep you get as you’re growing also play a role in determining your health.

The growth plates of your long bones fuse shortly after puberty. Once these bones fuse, there’s little you can do to change your height. Most guys reach their adult height in their late teens.