Height Calculator: How Tall Will My Child Be? (Adult Height Estimate)

Two ways to estimate adult height

This calculator shows two estimates side by side. The mid-parental method uses only the parents’ heights. The percentile method uses only the child’s own age, sex and current height. Each answers a slightly different question, so they often differ.

• Mid-parental height needs both parents’ heights.
• The percentile method needs the child’s age (2 to 20 years) and current height.
• If something is missing, the page shows the estimate it can and says what to add for the other.

Mid-parental (target) height

The American Academy of Pediatrics describes mid-parental height as the average of the parents’ heights with an adjustment for the child’s sex. For a boy, add 13 cm to the mother’s height, then average it with the father’s. For a girl, subtract 13 cm from the father’s height, then average it with the mother’s. Both versions give the same result as (father + mother ± 13 cm) ÷ 2.

One standard deviation of adult height around this target is about 5.1 cm, so the AAP gives a target range of ± 10.2 cm, two standard deviations. About 95% of children are expected to finish within that range. For example, with a father of 178 cm and a mother of 163 cm, the target is 177 cm for a boy and 164 cm for a girl, with a range 10.2 cm either side.

• The range is wide on purpose: about 20 cm (8 inches) from low to high.
• It describes children in general, not any one child.

What a percentile means

A growth chart percentile compares a child with others of the same sex and age. At the 25th percentile, about 25 of 100 children are shorter and 75 are taller. The CDC publishes the curves from tables of three numbers (L, M and S) for each age; this page uses those tables for ages 2 to 20 to turn a height into a z-score and a percentile.

The percentile method then asks what height sits at that same z-score at age 20. A child at the 40th percentile at age 7 is estimated to reach the 40th percentile adult height. That works only if the child stays on the same curve, which can change, especially during puberty.

• A percentile describes position among children measured by the CDC, not health. A doctor looks at the pattern of growth over time.
• The CDC curves in the chart are the 5th, 50th and 95th percentiles for the sex you choose.

Why the two estimates can differ

Parents’ heights say something about a child’s genes, while the percentile reflects the child today. They can disagree for ordinary reasons.

• Puberty timing: a child who starts puberty earlier can look tall for their age for a while and then slow down; a later start can do the opposite. Percentile moves during these years, roughly 9 to 15.
• Parents who are far from average: the mid-parental method shifts the estimate toward the parents, while the percentile method does not look at them.
• Measurement: a small error in standing height moves the percentile, especially for young children.
• If the difference is large, or you have any growth concern, talk with a doctor; they can follow a child over time, which this one-time calculation cannot.