Tools · Child
Adult Height Predictor: How Tall Will My Child Be?
Enter both parents' heights to estimate your child's adult height using the mid-parental height formula, with the range the estimate actually carries.
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This article is for general information and is not a substitute for professional medical advice. Always consult your pediatrician or doctor about your child.
Sources: WHO, CDC, AAP and NHS guidance. Recommendations differ between countries — for local advice see the NHS or CDC.
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Enter both parents' heights to see the estimate.
What the calculator is doing
This is the mid-parental height method, the same arithmetic a paediatrician sketches on the back of a growth chart. Add the two parents' heights, adjust by 13 cm — up for a boy, down for a girl — and halve the result. The 13 cm stands for the average adult height difference between men and women, so the adjustment is a way of asking what each parent's height would have been had they been the child's sex.
The number it returns is a midpoint, and a midpoint on its own is misleading. That is why the second box shows a range of roughly 8.5 cm either side. Most children land inside that band, and the band is wide because adult height is polygenic: each parent passes on many height-related genes, and their own height is only a partial summary of what they carry. Two parents of identical height routinely have children who end up several centimetres apart.
The estimate is weakest at the edges. When the parents are very tall, very short, or far apart from each other, real outcomes drift back toward the population average more than the formula suggests. Everything here is calculated in your browser; no heights are stored or sent anywhere.
What it cannot tell you
It cannot tell you whether your child is growing well. That question is answered by a growth curve, not by a prediction: a child is plotted at each visit and what matters is whether they keep tracking along the same percentile line. A child can sit far from the mid-parental estimate and be perfectly healthy, and a child can sit right on it while their curve is drifting downward. The curve is the signal; the prediction is background.
It also cannot see the things that hold growth below its potential — long-running undernutrition, untreated coeliac disease, some hormone conditions, chronic illness, severely disrupted sleep. Several of those are treatable, which is the real argument for regular measurement: the point is to notice a change in the curve early, while something can still be done. If your child's growth has changed pattern, that is a conversation for your paediatrician rather than for a page of arithmetic.
And it says nothing about timing. Two children with the same adult height can arrive there on very different schedules — one growing steadily, the other staying small and then moving quickly through puberty. A child who is currently the shortest in the class may finish taller than most of them.
Frequently Asked Questions
How is mid-parental height calculated?
Add both parents' heights in centimetres. For a boy, add 13 cm to that total; for a girl, subtract 13 cm. Divide the result by two. The 13 cm is the average adult height difference between men and women, so the step is really asking what each parent's height would have been had they been the child's sex. The answer is a midpoint, not a prediction of one exact number.
How accurate is this estimate?
Roughly speaking, about two thirds of children end up within 5 cm of the midpoint and most within 8.5 cm either side, which is why the calculator shows a range rather than a single figure. A range that wide is not a flaw in the arithmetic — it reflects how much of adult height is decided by things the formula cannot see: nutrition, sleep, chronic illness, timing of puberty, and the many genes each parent contributes that are not captured by their own height.
Does the formula work if the parents are very different heights?
It becomes less useful. The formula assumes the child sits between the parents, and when the two heights are far apart the midpoint describes neither of them well. It is also weaker at the extremes: for very tall or very short parents, the estimate tends to pull toward the population average rather than following the parents exactly. Treat a wide-gap result as a rough bracket, not a target.
My child is far off the predicted line. Should I worry?
Not on its own. A single height measurement says very little; what a clinician watches is the growth curve over time. What is worth raising is a change in pattern — a child who was tracking along one percentile line and has drifted downward across several, or one who has stopped growing at the rate they were. That conversation belongs with your paediatrician, who can measure properly and look at the whole picture. This page cannot do any of that.
Can anything change a child's adult height?
Genetics sets most of it, but not all. Long-running undernutrition, untreated coeliac disease, chronic illness, some hormone conditions, and severely disrupted sleep can all hold growth below its potential, and several of those are treatable. That is the argument for regular growth monitoring rather than for any particular intervention: the point of plotting a child on a chart is to notice a change early, while there is still something to be done about it.
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