Baby height predictor
For a baby or toddler, the most useful adult height estimate comes from the parents: (father + mother) ÷ 2, plus 6.5 cm for a boy or minus 6.5 cm for a girl, with a range of about ±8.5 cm. A baby’s own length says little about adult height, because infants often move up or down the growth chart in the first two years. Enter the parents’ heights below. An estimate, not medical advice.
Baby and parents
Optional: the “double at age 2” rule
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Estimated adult height
Enter both parents’ heights and the baby’s sex, then press Estimate adult height.
How tall will my baby be?
Nobody can say precisely. What can be said is where the genetics point. The parents-only estimate above is the same mid-parental formula pediatricians use as a quick reference; the dedicated mid-parental height calculator shows each step. Its range is wide, about 17 cm from bottom to top, and that width is honest: at this age there is not enough information for anything tighter.
The “double the height at age 2” rule
A popular shortcut says adult height is roughly twice the height at age 2 (some versions use 18 months for girls). It is easy to remember, and it is in the right general area for many children. We could not find a published error range for it, so this page does not quote one. Use it for fun, and give more weight to the parents’ estimate.
What matters in the baby years: following a curve
Rather than aiming at an adult number, pediatricians watch whether a baby follows a consistent growth curve. A baby who steadily tracks the 40th percentile is usually growing well, whatever the exact figure. From age 2 you can check a height with the height percentile calculator. A sudden move across percentile lines is something to raise with your pediatrician.
When prediction gets better
From age 4 the Khamis-Roche calculator can add the child’s own height and weight to the parents’ heights, which narrowed the error band in the original study to about ±4–5 cm for 90% of children. The main height predictor switches to it automatically once the age is 4 or more.
Common questions
- Does birth length predict adult height?
- Only weakly. Size at birth reflects conditions in pregnancy as much as genetics, and many babies change percentile in the first two years.
- Is the estimate different for boys and girls?
- Yes. The same parents give a target 13 cm higher for a son than for a daughter.
- My baby is very long or very short for their age. Should I worry?
- A calculator cannot answer that. Your pediatrician can, by looking at the trend across several check-ups.
Source: Tanner JM, Goldstein H, Whitehouse RH. “Standards for children’s height at ages 2–9 years allowing for height of parents.” Archives of Disease in Childhood. 1970;45:755–762. See About for all citations.