How tall will my child be?
From age 4 to 17½, a child’s height, weight and age and both parents’ heights predict their adult height to within about 2 in, 9 times in 10: that is the Khamis-Roche method, built on children measured every six months until they stopped growing. For a baby or a toddler, the parents’ heights alone give the usual target, a wider range.
Your child’s adult height
Example: an 8-year-old girl, 4 ft 2 in and 56 lb, with a mother of 5 ft 5 in and a father of 5 ft 10 in. Type your own over it.
This girl will probably grow to about 5 ft 5 in (165.5 cm).
9 times in 10, the method lands within 1.7 in (4.3 cm) of the adult height: here, 5 ft 3.5 in (161.3 cm) to 5 ft 7 in (169.8 cm).
From the parents’ heights alone, the usual target for a girl is 5 ft 5 in (165 cm), and most children end up within 8.5 cm (3.3 in) of it: 5 ft 1.5 in (156.5 cm) to 5 ft 8.5 in (173.5 cm).
How the prediction works
The Khamis-Roche method is a set of equations, one for each half year of age from 4 to 17½, for boys and for girls. Each multiplies the child’s height, weight and the parents’ average height by its own numbers and adds them up. Alex Roche and Harry Khamis built it in 1994 from the Fels Longitudinal Study, which measured children in southwest Ohio every six months into adulthood. It needs no X-ray of the hand, which the older methods did, and it is only a little less accurate than they are. The published table had misprinted weight numbers, corrected by the journal in 1995; this calculator uses the corrected ones.
The parents’ target is older and simpler: add the mother’s and father’s heights, add 13 cm (5 in) for a boy or take 13 cm away for a girl, and halve the total. James Tanner set it out in 1970, with most children landing within 8.5 cm (3.3 in) of it. It works at any age, even before birth, but it knows nothing about how the child is growing.
How sure is it?
For boys, 9 predictions in 10 land within 2.1 in (5.3 cm) of the adult height; for girls, within 1.7 in (4.3 cm). Half land within about 0.9 in for boys and 0.7 in for girls. The parents’ target is much looser: its range spans 17 cm (6.7 in).
The equations were built from white American children free of disease, so they fit other children less surely. A child who started puberty early or late, or who has a condition that affects growth, may end up well outside the range. Children of very tall or very short parents also tend to land a little closer to average than the parents’ target says. If your child’s growth worries you, ask their doctor: a growth chart over several visits says far more than one prediction.
Where your child stands today
To see how your child’s height compares with other children of the same age, use the height percentile for children and teens, from the CDC growth charts. For the most accurate numbers, measure the height barefoot against a wall, at the same time of day each time.
The equations: Khamis and Roche, Pediatrics 1994, with its 1995 erratum. The parents’ target: Tanner, Goldstein and Whitehouse, 1970; its range: Accurate prediction of children’s target height from their mid-parental height (2024). Children’s heights by age: CDC 2000 growth charts, stature-for-age.
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For the prediction method, cite the original publisher as well: Khamis and Roche, Pediatrics.