Height Calculator

This height calculator predicts how tall a child is likely to be as an adult, using the parents’ heights. It uses the mid-parental height method that doctors use alongside growth charts, and shows the result in feet and inches and in centimetres, with a likely range.

Mid-parental height formula

  • Boys: (father’s height + mother’s height + 13 cm) ÷ 2, or + 5 inches
  • Girls: (father’s height + mother’s height − 13 cm) ÷ 2, or − 5 inches

The 13 cm (about 5 inches) reflects the average height difference between adult men and women. Most children end up within about 8.5 cm (3.3 inches) above or below this target.

Worked example

A father is 5 ft 10 in (70 in) and a mother is 5 ft 4 in (64 in). For a son: (70 + 64 + 5) ÷ 2 ≈ 69.5 in, or 5 ft 9½ in. For a daughter: (70 + 64 − 5) ÷ 2 ≈ 64.5 in, or 5 ft 4½ in.

What else affects height?

  • Nutrition and sleep during childhood and the teenage years.
  • Health conditions and some medicines that can slow growth.
  • Timing of puberty: early developers are often taller at first but end up near their predicted height.

When to talk to a doctor

A doctor plots a child’s height on a growth chart at each check-up. Talk to them if your child crosses percentile lines on the chart, grows much slower than others their age, or looks very different from the predicted range.

Frequently asked questions

How accurate is predicting height from parents?

It gives a target, not a guarantee. Most children end up within about 8.5 cm (3.3 inches) of the mid-parental height.

At what age do girls and boys stop growing?

Girls usually reach adult height around 14 to 16, and boys around 16 to 18, but it varies with the timing of puberty.

Can a child be taller than both parents?

Yes. Height is shaped by many genes plus nutrition and health, so a child can be taller or shorter than both parents.

Does the doubling-height-at-age-2 rule work?

It is a rough rule of thumb: boys at 2 and girls at about 18 months are often near half their adult height. The parents’ heights method is usually preferred.

Related calculators

Sources

Last reviewed: October 2026. For information only; not medical advice. Talk to a doctor about your child’s growth.

Scroll to Top