How Tall Will My Child Be?

Michele Meleen
measuring childs height

Parents often wonder what their kids will look like when they grow up, and kids ponder how big they might be one day. While there's no surefire way to determine how tall your child will grow to be, there are well-known formulas that can give you a good idea.

Height Formulas

Using basic math skills and a few family measurements, doctors or parents can determine the relative adult height of any child. Genetics and current growth are big factors in a child's physical development, so they often serve as the basis for predicting adult height.

Mid-Parental Method

Dr. Jay L. Hoecker says this is the most popular method pediatricians and parents use to predict a child's adult height. One of the reasons this method is accurate is because height is largely determined by genetics.

  1. Choose one form of measurement to use throughout, either inches or centimeters.
  2. Add the child's mother's height to the child's father's height.
  3. If predicting how tall a boy will be, add either five inches or 13 centimeters to the last number. If predicting how tall a girl will be, subtract five inches or 13 centimeters.
  4. Divide the number you obtained in step three by two to get the predicted height of your child.

Two Times Two Method

A simpler formula, the Two Times Two method involves measuring a child's height at a specific age. If you're asking yourself "How tall will my daughter be?" Dr. Hoecker shares that all you have to do is take her height at age 18 months and double it. To find out "How tall will my son be?" you'll need to double his height at age two.

Khamis Method

For older kids ages four to seventeen, Dr. Alex Roche created a research-based mathematical equation for predicting adult height. The Khamis-Roche Calculator accounts for a child's sex, age, current height, and current weight along with the mother's and father's heights. This is considered one of the most accurate calculators available for height prediction in typical white children.

Bone Age

The most accurate way to gauge a child's future height is through an x-ray. The internal image of the child's hand shows trained professionals the "bone age" of a child. These images are then compared to those of other children of a similar age and gender, according to KidsHealth. The entire procedure takes only a few minutes, and then a radiologist can read the results and send them to your child's regular doctor. Parents should be aware that bone age x-rays are typically used to evaluate a child's bone growth and diagnose any possible conditions related to his or her physical development.

Shoe Size Method

A common, but unreliable, way to predict your child's height is to double the length of their foot at age one. The resulting number is said to be their adult foot size. While any person's foot size is typically proportional to their height, there is no solid formula that accurately predicts height from shoe size.

Follow the Curve Method

Pediatricians use growth charts with percentile ranks to help determine if your child's development is following the typical curve for his age and size. You can also use these to predict future height. Find your child's current height on the age-appropriate growth chart from the Centers for Disease Control. Follow along that same percentile curve into adulthood to see their projected height. As with many methods, this one will only give you a ballpark estimate.

Other Determining Factors

Expert pediatricians from Healthychildren.org share there are many factors, both genetic and environmental, that influence each method of height prediction.

Grandfather compares grandmother and grandsons height

Family History

Dr. Roche found that about 70 percent of growth is determined by genetics and gender, so it's no wonder parental height is often a factor in these calculations. Growth patterns can also be shared among family members. Things like when each parent experienced puberty or growth spurts can help predict when a child will also do so.

Nutrition

The nutrients a child receives help his or her body grow and develop in a healthy manner. Kids who don't get appropriate vitamins and minerals or who are underweight or overweight can experience heights uncharacteristic of their age, family member height, and potential adult height. Diet, exercise, and sleep patterns can also impact a child's growth.

Medication

Chronic ingestion of some medications, like prednisone, can contribute to slowing a child's growth. Some studies suggest antibiotic use has a growth-promoting effect while others show that medications prescribed to treat ADHD may suppress growth.

Genetic Conditions

If a child has a genetic disorder, this can differentiate their height expectations from those of parents and other family members. For example, kids with Down Syndrome are often shorter than their parents.

Make a Strong Prediction

Whether you're wondering how tall your child might be, or he or she is asking, these methods can help you make an educated guess. Keep in mind that while many height prediction methods are very accurate, none are 100 percent.

How Tall Will My Child Be?