Predicting Adult Height: The Mid-Parental Formula for Boys and Girls
October 29, 2026
Height is strongly inherited, and a simple formula based on the parents' heights gives a reasonable estimate. The mid-parental height method: for a boy, adult height ≈ (father's height + mother's height + 13 cm) ÷ 2; for a girl, (father's height + mother's height − 13 cm) ÷ 2. In inches, use 5 inches instead of 13 cm.
Example: father 180 cm, mother 165 cm. Boy: (180 + 165 + 13) ÷ 2 = 179 cm. Girl: (180 + 165 − 13) ÷ 2 = 166 cm. In inches: father 70 inches and mother 64 inches. Boy: (70 + 64 + 5) ÷ 2 = 69.5 inches. Girl: (70 + 64 − 5) ÷ 2 = 64.5 inches.
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About 95% of children end up within roughly ±8.5 cm (±3.3 inches) of the estimate. So the boy in the example is likely to be between about 170.5 and 187.5 cm. Siblings can differ a lot, as each inherits a different mix of genes. The formula works best for children in healthy environments. Other predictors use the child's current height and bone age (from a hand X-ray), which are more accurate for individual cases. Doubling the height at age 2 is a rough rule for boys (and a bit less for girls, who reach half their adult height at about 18 to 20 months).
| Father | Mother | Boy (est.) | Girl (est.) |
|---|---|---|---|
| 180 cm | 165 cm | 179.0 cm | 166.0 cm |
| 175 cm | 160 cm | 174.0 cm | 161.0 cm |
| 70 in | 64 in | 69.5 in | 64.5 in |
| 72 in | 66 in | 71.5 in | 66.5 in |
What Else Affects Adult Height
Nutrition in childhood, chronic illness, sleep, hormonal conditions, and the timing of puberty influence the final height. Children who start puberty early may be taller at 12 to 13 but end up average; late developers grow for longer. Boys typically grow until about 16 to 18 and girls until about 14 to 16, and growth plates close afterward. Height trends over generations have increased in many countries because of better nutrition.
Growth Charts and Percentiles
Pediatricians plot a child's height on a growth chart. A child who follows the 75th percentile curve is likely to keep that track; crossing percentile lines downward or sudden changes deserve a conversation with a doctor. Percentiles describe how a child compares with others of the same age and sex, and the mid-parental height can be compared to the child's percentile to see if the growth is consistent with the family's pattern.
Caveats
This is an estimate, and it doesn't replace medical evaluation. If a child is much shorter or taller than expected, or growth slows, consult a pediatrician. Height has no bearing on worth.
Frequently Asked Questions
What is the mid-parental height formula for a boy?
(Father + mother + 13 cm) ÷ 2.
What is it for a girl?
(Father + mother − 13 cm) ÷ 2.
How accurate is it?
About 95% fall within ±8.5 cm.
What other factors matter?
Nutrition, health, hormones, and the timing of puberty.
Can the formula predict an individual child exactly?
No, it only gives an estimate with a range.