Mid-Parental Height Calculator: Child’s Genetic Target Height
Predict a child’s adult target height from both parents’ heights with the Tanner mid-parental method: (mother + father ± 13 cm) ÷ 2, with the ±8.5 cm (about 95%) target range, in cm and feet and inches, for a boy and a girl.
How it works
Boy: (mother + father + 13 cm) ÷ 2 · Girl: (mother + father − 13 cm) ÷ 2 · Target range = result ± 8.5 cm (about ±2 SD) · In inches: ± 5.12 in instead of 13 cm (often rounded to 5 in), range ± 3.35 in
The mid-parental height (Tanner, 1970) estimates a child’s genetic target height from the parents’ heights. Adult men are on average about 13 cm (5.12 in) taller than adult women, so the method first puts both parents on the child’s sex: for a boy add 13 cm to the mother’s height, for a girl subtract 13 cm from the father’s, then average the two. Equivalently, add or subtract 6.5 cm (2.56 in) to the parents’ average. Height is strongly inherited but not exactly, so the result is a range. The usual target range is ±8.5 cm (±3.35 in), about two standard deviations, which covers roughly 95% of children; about two-thirds land within ±4.25 cm. Paediatricians plot the target on the growth chart to see whether a child is growing in line with the family. Enter heights in cm or inches; the advanced option switches to the rounded 5-inch adjustment some US sources use. The result is less reliable when a parent is very tall or short, when a parent’s own growth was affected by illness, and in children with growth disorders.
Worked example
With the defaults, a mother of 163 cm and a father of 178 cm: for a boy, (163 + 178 + 13) ÷ 2 = 177.0 cm (5′ 9.7″), target range 168.5 – 185.5 cm (5′ 6.3″ to 6′ 1.0″). A girl of the same parents would have a target of (163 + 178 − 13) ÷ 2 = 164.0 cm (5′ 4.6″).
Sources: MSD Manual: Height potential, a child’s target height based on midparental height (Tanner 1970; ±8.5 cm) · Miniwebtool child height predictor: mid-parental formula and worked example · Calculator.net height calculator (Khamis-Roche and parental-average methods)
Frequently asked questions
How do you calculate mid-parental height?
Add the parents’ heights, add 13 cm for a boy or subtract 13 cm for a girl, and divide by 2. In inches use 5.12 (often rounded to 5). For a mother of 160 cm and a father of 175 cm: a boy’s target is 174 cm and a girl’s 161 cm.
How accurate is the mid-parental height?
About 95% of children reach an adult height within ±8.5 cm (±3.35 in) of the target, and about two-thirds within ±4.25 cm. It ignores nutrition, health and chance, and works less well when a parent is very tall or short.
Why add 13 cm for boys and subtract it for girls?
Adult men are on average about 13 cm taller than women. Adding it to the mother’s height (for a boy) or subtracting it from the father’s (for a girl) puts both parents on the child’s sex before averaging.
Is there a more accurate height predictor?
For children aged about 4 to 17, the Khamis-Roche method uses the child’s current height, weight and age plus the parents’ heights, and bone-age methods use a hand X-ray. They predict more tightly than the parents’ heights alone.
What if my child is tracking well below the target range?
A child whose height is clearly below the family target range on the growth chart, or who is falling across centiles, should see a paediatrician to look for treatable causes such as nutrition problems, thyroid or growth hormone issues.
Related calculators
Educational estimate only. Mid-parental height gives a genetic target range, not a guarantee; a doctor uses it with the child’s measured growth on a growth chart. See a paediatrician if a child is crossing growth centiles, is very short or tall for the family, or is growing unusually fast or slow.