How this calculator works
The mid-parental height method, described by pediatric growth researcher James Tanner in 1970, is the simplest and most widely used way to estimate a child's likely adult height using only both parents' heights. It has been a standard part of pediatric growth assessment for decades, alongside — not instead of — plotting a child's own growth on a percentile chart over time.
The method starts from the average of both parents' heights, then shifts it up or down by roughly half the average adult height gap between men and women, to account for the child's own sex. The result is only a starting estimate: actual adult height depends heavily on genetics beyond just parental height, nutrition, general health during childhood, and puberty timing, so the honest range around any mid-parental estimate is wide — commonly cited as about ±8.5 cm, corresponding to roughly the 3rd to 97th percentile of outcomes.
This is a statistical estimate, not medical advice or a growth diagnosis. A pediatrician plots a child's actual measurements on a validated growth chart over time and can weigh factors — nutrition, chronic illness, puberty timing — that a two-input formula like this one has no way to account for.
The formula
Mid-parental height = (mother's height + father's height) ÷ 2Boy: predicted height = mid-parental height + 6.5 cmGirl: predicted height = mid-parental height − 6.5 cmTypical range: predicted height ± 8.5 cm (roughly 3rd-97th percentile)The 6.5 cm adjustment (13 cm total difference between the boy and girl estimates) approximates the average adult height gap between men and women. The ±8.5 cm range reflects how much individual outcomes vary even among children with the same parental heights.
Worked example: mother 165 cm, father 180 cm
- Average the parents' heights: (165 + 180) ÷ 2 = 172.5 cm.
- For a boy, add 6.5 cm: 172.5 + 6.5 = 179 cm predicted adult height.
- For a girl, subtract 6.5 cm instead: 172.5 − 6.5 = 166 cm predicted adult height.
- Either estimate carries a realistic range of about ±8.5 cm — so the boy's likely range is roughly 170.5 to 187.5 cm, not a precise number.
Frequently asked questions
How accurate is the mid-parental height method?
It is a rough, population-level estimate, not a precise prediction for an individual child. The commonly cited ±8.5 cm range covers most outcomes but is wide enough that a child could reasonably land well above or below the point estimate while still being entirely typical.
Does this account for nutrition or health conditions?
No. The formula uses only parental height. Chronic illness, nutrition during childhood, growth hormone conditions, and puberty timing can all shift a child's actual adult height noticeably above or below the genetic estimate. A pediatrician tracking growth on a percentile chart over years gives a much better picture than this formula alone.
Is this the same as a bone-age or growth-chart prediction?
No. Clinical height prediction (used by pediatric endocrinologists) typically combines a growth chart, current height and growth velocity, and sometimes a bone-age X-ray. The mid-parental method is a simpler, purely genetics-based starting point that doctors use alongside, not instead of, those tools.
Does the method work the same for every population?
The original formula was developed decades ago on specific study populations, and some later research has found it under- or overestimates final height in certain populations. Treat the result as a general approximation rather than a population-specific guarantee.
Can I use this before my child is born?
Yes — the mid-parental method only needs both parents' heights, not any measurement of the child, so it works the same whether the child is a newborn, a toddler, or not yet born. It is still only a rough, wide-range estimate (about ±8.5 cm) at any age, and a pediatrician's growth-chart tracking becomes more informative once actual measurements are available.