Child Height Predictor Calculator
Predict a child's adult height from their parents, with the range they are likely to finish in.
The child and their parents
Height prediction from parents is a rough guide, not a growth assessment. If you are worried about a child's growth, a paediatrician plotting them on a CDC or WHO growth chart over time will tell you far more than any single formula, the shape of the curve matters more than one point on it.
This predicts a child's adult height from the parents' heights, using the mid-parental method.
The prediction comes with a range of about four inches either way, which is the honest width of the estimate.
How adult height is predicted
The mid-parental method predicts adult height from the parents' heights. Average the two, then add 2.5 inches for a boy or subtract 2.5 for a girl.
A father of 5'10" and a mother of 5'4" give a predicted 5'9.5" for a son and 5'4.5" for a daughter.
The number that matters most is the one usually left off: the prediction carries a range of about four inches either way. So that son is predicted somewhere between 5'5.5" and 6'1.5". Genetics accounts for the large majority of adult height, and the rest — nutrition, health, sleep, timing of puberty — moves it within that window.
The single figure is the middle of an eight-inch band. Two siblings with the same parents routinely finish several inches apart.
What to enter
- Father's height
- Actual measured height, not what he reports. Self-reported heights skew upward.
- Mother's height
- Same. Both parents contribute roughly equally to the prediction.
- Child's sex
- Adds or subtracts 2.5 inches, reflecting the average adult height difference.
- Child's current height and age
- Optional, and useful for tracking growth percentiles, which say more than any single prediction.
What this assumes
The method assumes typical growth and nutrition. Chronic illness, endocrine conditions and severe undernutrition all affect final height.
It says nothing about growth timing. Early and late developers follow very different curves to similar destinations.
How to calculate your child's predicted adult height
Average the parents, adjust for sex, then apply the range.
- heights
- In inches, both measured rather than reported
- 5 inches
- Twice the 2.5 in sex adjustment, folded into the average
Measure both parents properly. Without shoes, standing straight against a wall. Self-reported heights are consistently too high.
Add them together with the sex adjustment. Boys: father + mother + 5. Girls: father + mother − 5.
Divide by two. 70 + 64 + 5 = 139, ÷ 2 = 69.5 in, which is 5'9.5".
Apply the ±4 inch range. That gives 65.5-73.5 in. The range is the honest answer; the midpoint is just its centre.
See a worked example: a son and a daughter, same parents
- Father
- 70 in, which is 5'10"
- Mother
- 64 in, which is 5'4"
Son: (70 + 64 + 5) ÷ 2 = 69.5 in, or 5'9.5". Range 65.5-73.5 in.
Daughter: (70 + 64 − 5) ÷ 2 = 64.5 in, or 5'4.5". Range 60.5-68.5 in.
Both ranges are eight inches wide, which is why siblings with identical parents often differ substantially.
Growth percentile tracking over time is more informative than any single prediction, because it shows whether a child is following their own curve.
5'9.5" and 5'4.5", each ±4 inches
Frequently asked questions
It gives a reasonable central estimate with a range of about four inches either way, so an eight-inch window in total.
That width is not a flaw in the method; it reflects genuine variation. Height is influenced by many genes plus environment, and siblings with the same parents often finish several inches apart.
The large majority. Twin and family studies typically put the heritability of adult height around 80%, meaning most of the variation between people in similar environments is genetic.
The remainder is nutrition, childhood illness, sleep and hormonal factors. Those matter most where nutrition is inadequate; in well-nourished populations genetics dominates.
Nothing raises the genetic ceiling. What good nutrition, adequate sleep and treating chronic illness do is ensure a child reaches their potential rather than falling short of it.
There is no supplement, stretch or exercise that adds height. Claims otherwise are marketing.
Girls typically finish around 14-16 and boys around 16-18, when the growth plates close. Boys grow for longer, which is most of the adult height difference.
Growth is not steady. The pubertal growth spurt is rapid and its timing varies widely, which is why a child's height relative to their peers can change a lot over a couple of years.
Not necessarily. The ±4 inch range is wide, and being at the lower end is common. Late developers can catch up substantially during puberty.
What is worth raising with a doctor is a child crossing downward through growth percentiles over time, rather than tracking steadily along a low one. That pattern is the meaningful signal.
Generally yes. A percentile chart shows whether a child is following a consistent curve, which is far more informative than a single-point prediction eight inches wide.
A child steadily on the 25th percentile is growing normally. One who drops from the 50th to the 10th over two years is worth investigating, regardless of what any prediction said.
Problems people actually run into
Treating the midpoint as a prediction
The estimate has a ±4 inch range, so 5'9.5" really means somewhere between 5'5.5" and 6'1.5".
Parents who fix on the single figure are frequently surprised. The range is the actual answer, and quoting it avoids a lot of unnecessary worry.
Comparing against peers rather than against the child's own curve
Puberty timing varies by years. A late developer can be well below classmates at 13 and above them at 17.
Track your child against their own percentile curve over time. Consistency along a curve is what matters, not where that curve sits relative to the class.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Last updated: September 4, 2026