Growth Science
Our mid-parental height calculator estimates a child's genetic target from the parents' heights, and our familial short stature guide covers healthy kids who are short because their parents are. This piece steps back to the question behind both: how much of height is actually genetic? It covers what the famous "80%" figure really means, how much of it scientists have traced to specific DNA, and why whole countries have grown several inches taller in a century without any change in their genes.
How Much Height Variation Do Genes Explain?
Twin-study heritability by age, compared with the share traced to specific DNA variants
What "80% Genetic" Actually Means
Heritability is the share of the height differences within a population that line up with genetic differences. If heritability is 80%, most of the reason people in that group differ in height is that they differ in DNA.
It does not mean 80% of your child's inches came from genes and 20% from food. Every inch depends on both. And because it's measured within one population and era, it can change when living conditions change.
Twin studies estimate heritability by comparing identical twins, who share essentially all their DNA, with fraternal twins, who share about half. If identical twins are much more alike in height than fraternal twins raised in the same home, genes must be driving much of the difference. The largest analysis of this kind pooled 45 twin cohorts from 20 countries and found heritability was lowest at age 1 (40% in boys, 38% in girls), rose through childhood to generally above 70% by late childhood, and peaked in adolescence at up to 83% in boys and 76% in girls.
The early-childhood pattern is worth noticing. At age 1, environmental factors shared by twins in the same family explained almost half of height variation (48% in boys, 49% in girls). That share shrank with age but never fully disappeared before adulthood, which the researchers interpreted as a sign that adult height still reflects childhood living conditions. The study also found that heritability was roughly similar across Europe, North America and Australia, and East Asia, even though average heights differed between those regions.
Thousands of Genes, Each With a Tiny Effect
There is no single "height gene." Height is polygenic, meaning it's shaped by thousands of genetic variants that each nudge it up or down by a tiny amount. The most recent mapping effort shows how many it takes.
Each child gets a new mix of both parents' variants
Spread across about 21% of the genome
No single variant decides height on its own
In European ancestry; much less in other ancestries
That 2022 study found the 12,111 variants cluster in 7,209 regions covering about a fifth of the genome, and together they account for nearly all of the heritability that common variants can capture. Yet even this saturated map explains about 40% to 45% of height variation in European-ancestry populations, well short of the roughly 80% suggested by twin studies. Part of the remaining gap likely lies in rarer variants that these methods don't capture well. The map also works much less well in people of non-European ancestry, explaining only around 10% to 20%, mainly because most participants in genetic studies to date have been of European descent. The authors noted that more research in other ancestries is needed to reach the same level of coverage.
What this means for predicting one child's height. Even with millions of participants, DNA explains less than half of height variation in the best-studied populations, and twin-based heritability is an average across a population, not a forecast for an individual. That's why no genetic test or formula can give an exact adult height. Rare single-gene and chromosomal conditions can have a large effect on height, which is one reason doctors evaluate children whose growth is far from what their family history would suggest, but for the vast majority of children, height reflects thousands of small genetic nudges plus the environment they grow up in.
Same Genes, Taller Generations
The clearest evidence that environment matters comes from history. Gene pools change very slowly, yet average heights in many countries changed dramatically within a few generations.
The NCD Risk Factor Collaboration reanalyzed 1,472 population-based studies covering more than 18.6 million people born between 1896 and 1996 in 200 countries. The biggest gains were in South Korean women and Iranian men, at 20.2 cm and 16.5 cm. Dutch men born in the last quarter of the 20th century became the tallest population in the dataset, averaging more than 182.5 cm. In contrast, adult height changed little over the century in some sub-Saharan African countries and in South Asia. Our average height by country ranking shows where populations stand today.
This is how height can be highly heritable and highly responsive to environment at the same time. Within a group of children who all have good food and health care, most of the remaining differences come from genes, so heritability looks high. Across generations or between countries with very different living conditions, environment can shift the entire average.
What Shapes the Rest
Within a well-fed population, the non-genetic share of height variation is smaller, but it's the part families can actually influence. Research points to the same handful of factors.
Why kids don't simply land between their parents. Because each child receives a new random mix of variants from both parents, siblings can differ noticeably in height, and children of very tall or very short parents tend to land somewhat closer to the population average. Our mid-parental height calculator explains how this "regression to the mean" and the steady rise in height across generations limit how precisely parents' heights can predict a child's adult height.
What This Means For You
The practical takeaway: height is highly heritable, with twin studies putting genetics behind up to about 80% of the differences between people by adolescence, spread across thousands of variants with tiny individual effects. But heritability describes variation within a population, not a fixed destiny, and a century of data shows environment can raise a whole population's height by several inches. For a sense of your child's genetic range, try our mid-parental height calculator; for healthy kids who are short like their parents, see our familial short stature guide; and to see how countries compare today, explore our height rankings by country. If growth seems off track, our guide on when to worry about a child's height explains the signs worth checking.
Frequently Asked Questions
Is height 80% genetic?
Roughly, by adolescence. A pooled analysis of 45 twin cohorts found that genes explained up to 83% of height variation in adolescent boys and 76% in girls, but only about 40% at age 1. The figure describes how much of the variation between people in a population traces to genetic differences, not how much of any one person's height comes from DNA.
Does height come from the mother or the father?
Both. Height is shaped by thousands of genetic variants inherited from both parents, and each child gets a different mix. That's why siblings can differ in height and why formulas that use both parents' heights give a range rather than an exact answer.
Can a child be taller than both parents?
Yes. Because each child inherits a new combination of variants, a child can end up taller or shorter than either parent. Better nutrition and health than the parents had growing up can also help, which is part of why many populations have grown taller with each generation.
Can a DNA test predict how tall my child will be?
Not precisely. The largest genetic study to date, with 5.4 million participants, found that 12,111 common variants explain about 40% to 45% of height variation in people of European ancestry and only about 10% to 20% in other ancestries. That leaves too much unexplained to predict an individual's adult height exactly.
If height is mostly genetic, why are people taller today than a century ago?
Because environment can shift a whole population even when genes don't change. Data on people born between 1896 and 1996 in 200 countries showed South Korean women gained 20.2 cm and Iranian men 16.5 cm on average, gains linked to improvements in nutrition, health, and living conditions rather than genetic change.
