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To predict your baby’s height, use the mid-parental method: add both parents’ heights in inches, add 5 inches for a boy (or subtract 5 for a girl), then divide by 2. The result estimates adult height within about 4 inches. Height is roughly 80% genetic, but nutrition, health, and sleep also shape the final number.
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The mid-parental height formula
The most widely used way to predict a baby’s adult height is the mid-parental (or “target height”) method:
- For a boy: (mother’s height + father’s height + 5 inches) ÷ 2
- For a girl: (mother’s height + father’s height − 5 inches) ÷ 2
The 5-inch adjustment reflects the average height difference between adult men and women. The estimate has a margin of roughly 4 inches either way, because height is polygenic — many genes combine, just like the traits in what will my baby look like.
Key takeaways
- Height is about 80% determined by genes.
- The mid-parental formula estimates within ~4 inches.
- Nutrition, sleep, and health influence the rest.
- Doubling a child’s height at age 2 is another rough guide.
A worked example
Say the mother is 64 inches (5’4″) and the father is 70 inches (5’10”). For a boy: (64 + 70 + 5) ÷ 2 = 69.5 inches, about 5’9.5″. For a girl: (64 + 70 − 5) ÷ 2 = 64.5 inches, about 5’4.5″. The child’s likely adult height sits within roughly 4 inches of that midpoint.
How much is genetic?
Research suggests around 80% of height variation is explained by genetics, spread across hundreds of genes rather than a single “tall gene.” That’s why tall parents usually have tall children, but a child can still land taller or shorter than both parents through the luck of the genetic shuffle.
Other factors that affect height
The remaining ~20% comes from environment: balanced nutrition, good overall health, adequate sleep (growth hormone is released during deep sleep), and physical activity. Chronic illness or poor nutrition in childhood can reduce final height, while healthy conditions help a child reach their genetic potential.
The Easiest Way to Predict Baby Height
To predict baby height, use the mid-parental formula — average both parents’ heights and adjust for sex — remembering genes set about 80% and a healthy environment the rest.
Frequently asked questions
Is it possible to predict baby height exactly?
No method can predict baby height exactly, but the mid-parental formula gets within about four inches of a child’s adult height.
How accurate is the mid-parental method?
It’s a solid estimate, typically within about 4 inches of actual adult height, but it’s not exact.
Can a child be taller than both parents?
Yes. Because many genes are involved, a child can inherit a combination that makes them taller (or shorter) than either parent.
Does the “double height at age 2” trick work?
It’s a rough rule of thumb — doubling a child’s height around age 2 gives a ballpark adult height, but with a wide margin.
Curious about your baby’s whole blend, not just height? Try the MixMyBaby generator, or read more on growth at MedlinePlus: Is height determined by genetics?