Predicted Height

Dear Lisa,

Is there any way to know what my baby’s adult height will be? My husband is really tall and I am wondering if my son is going to be tall too.

“How tall is he going to be?”

Dear “How tall is he going to be?”,

An infant’s height is influenced by its prenatal environment and gestational age (whether it was born on time or not). If your baby is in the 100 percentile for height at 6 months old, it does not necessarily mean that he will be in the 100 percentile for height when he is an adult. Height measurements under the age of two do not correlate with the predicted adult height of a child. Once your baby turns two years old there is a calculation that is used to predict adult height. Generally speaking, a child attains 50% of its adult height at two years old. Therefore, if you take your child’s height in inches at two years old and multiply it by 2, you will get his predicted adult height. For example, if your child is 35 inches at 2 years old, it would be expected that he will be 35 times 2 = 70 inches or 5 foot 10 inches as an adult.

There is a calculation called the Midparental Height Formula that many health care providers use to predict a child’s height. To determine a child's midparental height first you take the biologic father’s height in inches and add it to the biological mother’s height in inches. Take this number and subtract by 5 for girls or add by 5 for boys. If you divide this number by two you will get your child’s predicted height in inches.

For example if you want to figure out a baby boy’s predicted height, first accurately determine the biological parent’s height. If the mom’s height is 5 feet and 4 inches and dad’s height is 5 feet and 11 inches, you would first convert the height into inches. Since there are 12 inches in a foot, the mother would be 64 inches tall and the father would be 71 inches tall. Next take these two numbers and add them together, 64 + 71 = 135. Since the baby is a boy, add 5 to that number, 135 + 5 = 140. Divide 140 by 2 and you get 70. Therefore it is predicted that the boy will be 70 inches or 5 foot 10 inches when he is an adult. Depending on the child’s health and nutritional status, this value may vary 1 to 2 inches from the predicted height.

Have fun!

Lisa Kelly R.N.,P.N.P., C.
Certified Pediatric Nurse Practitioner

Pediatric Advice about Keeping Kids Healthy