How tall will my child be?

How the prediction works

1. The parents. Height is about 80% genetic. We start from the mid-parental height (the parents' average, plus 6.5 cm for a boy or minus 6.5 cm for a girl), then pull it 20% toward the population average. Very tall or very short parents tend to have children a little closer to average, which Francis Galton noticed back in 1886.

2. Your child today. If you enter their age and height, we find their percentile on the CDC growth charts. Children tend to stay near their percentile, so the older they are, the more their own height counts.

3. Everyday life. Food, dairy, vitamin D, sleep, stress at home, screens, sport and sugary drinks. Each answer moves the path by a modest amount, based on studies (sources below). Only the growing still to come can change: at 15, there's little left to play with.

4. Weight. The weight path starts from the parents' weight (children of two parents with obesity are much more likely to have obesity themselves) and the child's own weight, then the habits that matter most for weight: screens, sugary drinks, sleep and activity.

Height predictor methods compared

• Based on parents (mid-parental height). Works before birth and for newborns and infants. About 7 cm (3 in) either way for most children.
• Parents plus growth chart. What this calculator does once you add your child's age and height. It gets steadily more accurate as your child grows.
• Khamis-Roche. Uses the parents, the child's height and weight, for ages 4 to 17. Accurate to about 5 cm (2 in) on average, but built on white American children only.
• Bone age. An X-ray of the hand, read by a doctor. The most accurate adult height prediction, used when a doctor is worried about growth.

No height predictor is 100 percent accurate: genes are shuffled at every birth, so brothers and sisters can end up 10 cm apart.

Myths, checked

• Swimming or basketball makes kids tall. No: tall kids get picked for the team.
• Coffee stunts growth. No, it's a myth. It does spoil sleep.
• Hanging from bars or stretching adds height. Only for the rest of the afternoon: spines compress again by bedtime.
• More vitamin D means taller. Only if they're deficient. Rickets stunts growth; topping up a healthy child doesn't add height.

Sources

• CDC growth charts (2000), height-, weight- and BMI-for-age reference data.
• Tanner, Goldstein and Whitehouse (1970), mid-parental height standards.
• Silventoinen et al. (2003), twin studies: heritability of adult height about 80%.
• de Beer (2012), meta-analysis of dairy trials: about 0.4 cm extra growth per year during supplementation.
• Ganmaa et al. (2023), large randomised trial of vitamin D in Mongolian schoolchildren: no effect on height in children who were not deficient.
• Cappuccio et al. (2008), meta-analysis: short sleep linked to about 1.9 times the odds of childhood obesity.
• Malik et al. (2013), meta-analysis: sugary drinks and weight gain in children.
• American Academy of Pediatrics: no more than 1 hour of screen time a day for ages 2 to 5.

Questions parents ask

How accurate is a height predictor?

For a baby not yet born, the parents' heights predict adult height to within about 7 cm (3 inches) either way for most children. Once a child is a few years old, their own height on the growth chart narrows the range, and by the mid-teens most of the growing is done.

What is mid-parental height?

Average the parents' heights, then add 6.5 cm (2.5 in) for a boy or take 6.5 cm away for a girl. It is the classic genetic target, used by doctors since the 1970s.

Can you make a child taller?

Only within their genetic range. Good food, enough vitamin D and dairy help a child reach it. Nothing (stretching, swimming, basketball, supplements) pushes a healthy child beyond it.

Can I predict a newborn's adult height?

Yes, roughly, from the parents' heights. A famous rule doubles a boy's height at age 2 (a girl's at about 18 months), but it only works once they are toddlers. For a baby, the mid-parental height is the best estimate.

Does coffee stunt growth?

No. That's a myth. Coffee is still a bad idea for small children, but for sleep reasons, not height.