Child Height Predictor: The Mid-Parental Estimate
| Parents (father / mother) | Son's target | Daughter's target |
|---|---|---|
| 5'10" and 5'4" | 5'9½" | 5'4½" |
| 5'5" and 5'2" | 5'6" | 5'1" |
| 6'0" and 5'6" | 5'11½" | 5'6½" |
| 5'8" and 5'10" | 5'11½" | 5'6½" |
Pediatricians estimate a child's adult height the same way the American Academy of Pediatrics describes for parents at home: the mid-parental method, sometimes called Tanner's formula. Height is largely inherited, so the estimate starts from the biological parents' heights - add them together, divide by two, then shift up five inches for a boy or down five inches for a girl.
What the single number hides is the spread. Healthy children can land two to three inches either side of the mid-parental target and still be perfectly on their genetic curve - nutrition, sleep, and pubertal timing all move the outcome within that band. The only clinical-grade answer is a bone-age X-ray, which is why pediatricians reserve it for children whose growth actually looks off-track rather than for the family curious about the future.
How to use
- Measure both biological parents' heights in inches - or the adoptive parents' family heights, if those are the genetics in play - and enter them above.
- Select the child's sex: the formula shifts the parents' average up about five inches for boys and down about five inches for girls.
- Read the result as a target with a plus-or-minus two-to-three-inch band, and compare it against the pediatric growth chart percentile your child has been tracking - consistency of trajectory matters more than any single estimate.
Frequently asked questions
How accurate is the mid-parental height estimate?
It is a statistical center, not a measurement: most healthy children land within about two inches of the mid-parental target, roughly one in twenty wanders three inches or more, and the estimate is most reliable for children whose growth has been tracking steadily along one percentile line. It cannot see nutrition problems, hormonal conditions, or late bloomers - which is what the pediatrician's growth chart is for.
Does the child's current height matter to the prediction?
Not to the mid-parental formula itself, which works from genetics alone - but pediatricians read the two together. A child tracking at the 25th percentile while the parents' mid-parental target sits near the 25th percentile is reassuring; the same height above parents' target can prompt a closer look. Trajectory and target matching is the clinical signal.
Can two short parents have a tall child?
Occasionally, yes - the estimate is an average with a documented spread, and height genetics recombine: grandparents' height can resurface, and the two-to-three-inch band around the mid-parental target is where that lives. What it almost never does is jump far outside the band without a reason, which is precisely when doctors investigate rather than shrug.
Why does the formula shift five inches by sex?
The five-inch offset encodes the average adult height gap between men and women in the reference population - about five inches in the US. It is a population calibration, not a law of biology, and it is the reason the same parents produce predictions a notch apart for sons versus daughters before any individual variation begins.
When is a bone-age X-ray worth it?
When growth stops tracking its own curve, when a child is far outside the mid-parental band, or when puberty starts markedly early or late - the hand-and-wrist X-ray shows skeletal maturity, which combined with the growth chart tells an endocrinologist how much growing time remains. For the healthy, curious family, the mid-parental estimate plus the growth chart answers the question without any radiation.