Child Height Predictor

Curious to find out how tall your child will be when they grow up? We can't see the future, but with a little math and science, we can make a pretty good guess about how tall they'll be when they're 18 – with a margin of error under 2 inches.

This calculator works for children age 2 and up. (Depending on your child's age, we'll use some or all of the information you entered in our calculations.) You may get inaccurate results for children who are exceptionally tall or are already taller than both their parents.

The Height Predictor is meant to be a fun tool, and doesn't guarantee your child will be this height when they grow up. If you're concerned about your child's growth, talk to their healthcare provider.

How to tell how tall your child will be

There are a few different methods of predicting how tall your child will be when they grow up. Our Child Height Predictor tool uses the Khamis-Roche method, which is based on a study conducted in the 1990s with about 400 participants.

The method takes a child's height, weight, and the average height of their parents, then uses ratios to determine how to calculate the child's predicted height at age 18. A previous method also used the child's skeletal age, which is how mature a child's bones are and requires an X-ray. But the Khamis-Roche researchers wanted to find a way parents could predict their child's height without having to get an X-ray taken.

If you want to test out other ways to predict your child's height at home, these are a couple methods you can try:

Two years times two

Children grow a ton in their first few years of life – in fact, their first growth spurt from baby to toddler accounts for about half of their adult height. One simple way to predict how tall your child will be when they grow up is to take their height at age 2 if they're a boy or 18 months if they're a girl and double it. (Girls grow a little faster than boys.)

This method has been around for a long time, but there isn't any scientific research about how accurate it is.

Mid-parental method

Another way to estimate your child's adult height is to add together the height of both parents and divide it by two.

Then, some methods say to add 5 inches if they're a boy and subtract 5 inches if they're a girl; others say to only add or subtract 2 ½ inches. There's a high margin of error with this method – it could be off by 4 inches.