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Predicting a Child’s Adult Height

Parents often wonder how tall their toddler or preschooler might be when they grow up. Gradeschoolers and young teens may ask, "How tall will I be?" It is a natural question for parents and children, and besides being a little fun to try and predict how tall a child might be, pediatricians also find it helpful to make sure a child is growing as expected. While no one has a crystal ball, there are ways parents and pediatricians can make an educated guess. Read on.

How is a Child's Adult Height Predicted?

The most accurate method of height prediction comes from using a child's "bone age," determined by an X-ray of the hand, but there are several methods you can use at home to get an idea of how tall your child will eventually become. The most common way to estimate a child's adult height is to base it on the parents' heights.

Two Years Times Two Method

Did you know the earliest growth spurt, from baby to toddler, actually accounts for roughly half of a child's adult height? A simple method to predict adult height is to double the child's height at age 2. Girls develop more quickly, so doubling their height at 18 months old can also be used as an estimate of how tall they will be as adults. While this method has been around for a long time, no research exists to demonstrate its accuracy.

Mid-Parental Method

A slightly more complex method of predicting your child's height is known as the "mid-parental method." Add together the measured heights of the mother and father in inches and divide by 2.

  • For a boy: add 2½ inches
  • For a girl: subtract 2½ inches

Note: This is just a very rough estimate of the average height of how tall a child will be when fully grown. You can expect a margin of error of about four inches up or down. The taller the parents, the taller the child is likely to be; similarly, the shorter the parents, the shorter the child.

Growth Charts

Regular measurements of a child's height, weight and head size and plotting them on a growth chart are a good way to see if your child is growing as expected. Pediatricians use standardized growth charts at each well-child visit. What many people don't realize is that growth charts are also helpful for judging the onset of puberty in an older child. As you may know, puberty is occurring at an earlier age these days. The onset of pubic hair or breast budding in girls can occur normally as early as age six! Growth charts can help pediatricians determine whether your child's early development is in the normal range.

Family History & Genetics

Height and growth patterns usually run in families. Your child's pediatrician may ask about your own height, since your genetic make-up is the biggest factor in how your children grow. You may also be asked how tall other family members are. Additionally, you may be asked how fast and at what age you grew during your childhood (i.e. your growth pattern). Were you short in grade school but kept growing after all of your friends stopped? Did you go through puberty early or late? These may be important clues for your child's pediatrician.

What Else Affects Your Child's Height?

While genes play a huge part in predetermining how tall your child will be (e.g. short parents usually have short children) other factors have an impact on how much your child grows. These include:

  • Nutrition: A child who is overweight is often taller than classmates, although that does not necessarily mean that he will be taller as an adult. Children who are very underweight might be shorter than expected for age.
  • Hormones: Hormone imbalances, such as low thyroid or growth hormone levels, lead to slower than expected growth and can result in children who are either shorter or taller than would be expected if not diagnosed and treated. Review red flags to help you tell if your child is growing normally and will reach his predicted height or if he might have a growth hormone problem.
  • Medications: Some medications, particularly chronic use of corticosteroids (like prednisone), can slow growth.
  • Health conditions: Children with some chronic illnesses, such as severe arthritis, untreated celiac disease, or cancer may be shorter than expected.
  • Genetic conditions: Children with some genetic conditions can cause either short or tall stature. For example, those with Down Syndrome, Noonan Syndrome, or Turner Syndrome tend to be shorter than other family members, while Marfan Syndrome can cause someone to be taller. 

Additionally, exercise, pollution, sleep patterns, climate, fitness, diet, and psychological well-being can also impact growth.

If You Have Concerns about Your Child's Height:  

If you are concerned about your child's height or think that your child may be growing too fast or too slowly, talk to your pediatrician. If needed, your pediatrician can order further tests. A simple x-ray of the hand and wrist may show how much growth your child has left. Lab tests can also help find the cause of growth problems and how to treat them. You may also be referred to a pediatric endocrinologist, pediatric geneticist, or other pediatric specialist for further evaluation and treatment.

Don't delay!

Remember, once your child finishes puberty, growth stops. A short teenager has little or no time to catch up on growth, while a younger child still has time to be treated and grow taller.

Last Updated
Section on Genetics and Birth Defects (Copyright © 2015 American Academy of Pediatrics)
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.
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