Child Height Predictor (Mid-Parental)
Estimate how tall a child will grow from the parents’ heights (mid-parental target height and range), and from the child’s current height on the CDC growth chart.
How it works
Boy = (mother + father + 13 cm) ÷ 2 · Girl = (mother + father − 13 cm) ÷ 2 · Range = target ± 8.5 cm · Growth-chart projection: z = ((height ÷ M)^L − 1) ÷ (L × S) at the child’s age, adult height = M₂₀ × (1 + L₂₀ × S₂₀ × z)^(1/L₂₀)
The mid-parental method (Tanner) estimates a child’s genetic “target height” by averaging the parents’ heights and shifting by half the average difference between men and women: 13 cm, so +6.5 cm for a boy and −6.5 cm for a girl. You can change the difference under More options. The ±8.5 cm range is about two standard deviations, so roughly 95% of children finish inside it. If you also enter the child’s age (2–20) and current height, the calculator places the child on the CDC 2000 stature-for-age growth chart using the published LMS values. It assumes the child stays on that percentile and reads off the height at age 20. That second estimate uses the child’s own growth, but it is thrown off by early or late puberty. When the two estimates disagree a lot, the gap itself is the useful signal. The Khamis-Roche method, which also uses the child’s weight, and bone-age methods such as Bayley-Pinneau are more precise, but they need regression tables or an X-ray that a simple calculator cannot replace.
Worked example
For a boy with a 163 cm mother and 178 cm father: (163 + 178 + 13) ÷ 2 = 177 cm predicted adult height, with an expected range of about 168.5–185.5 cm (5′6″ to 6′1″). A sister would have a target of (163 + 178 − 13) ÷ 2 = 164 cm. If the boy is 8 years old and 132 cm tall, he sits around the 76th percentile on the CDC chart, which projects to about 182 cm at age 20. That is 5 cm above the mid-parental target and well within the range.
Sources: Tanner JM, Goldstein H, Whitehouse RH. Standards for children’s height at ages 2–9 years allowing for heights of parents. Arch Dis Child 1970 · CDC — 2000 growth charts, stature-for-age LMS data files · Barstow C, Rerucha C. Evaluation of short and tall stature in children. Am Fam Physician 2015
Frequently asked questions
How accurate is the mid-parental prediction?
It gives a reasonable ballpark. The ±8.5 cm range covers about 95% of children, and about two-thirds land within roughly ±4 cm of the target. It cannot account for the child’s own growth pattern, so a doctor tracking the growth curve over time will predict more precisely.
Why add or subtract 13 cm for sex?
On average adult men are about 13 cm taller than adult women. Adding 13 cm for a boy or subtracting it for a girl before halving shifts the parents’ average by 6.5 cm toward the child’s sex. Some references use 12.7 cm (5 inches) or 14 cm, which you can set under More options.
What does the growth-chart projection add?
It uses the child’s actual height for their age. The calculator finds the child’s percentile on the CDC stature-for-age chart and assumes they stay on it until 20. Children usually track their percentile from about age 2 to the start of puberty, so the projection is most useful before then and less reliable during the growth spurt.
Can a child grow taller than the predicted range?
Yes. The range covers most children but not all. Better nutrition than the parents had, genes from grandparents, or health conditions can push a child above or below it.
When should I talk to a doctor about my child’s height?
If the child is below the 3rd or above the 97th percentile, is crossing percentile lines on the growth chart, grows less than about 5 cm a year before puberty, or is tracking more than 10 cm below the mid-parental target. Those are the usual reasons for a growth check.
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This is a general educational estimate, not medical advice. Every child grows, feeds and responds to medicine differently — for anything about your child’s health, growth, nutrition or medication, follow the guidance of your pediatrician.