Predicted Adult Height Calculator (Mid-Parental Method)
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
The Tanner mid-parental method estimates adult height with (father's height + mother's height + 13) ÷ 2 for a boy, or (father's height + mother's height − 13) ÷ 2 for a girl. For a 180 cm father and a 165 cm mother, a boy is estimated at 179 cm (±8.5 cm), a girl at 166 cm (±8.5 cm).
Explanation
The mid-parental method, developed by pediatrician James Tanner, has been the reference formula used in pediatrics since the 1970s to estimate a child's likely adult height from just the two parents' heights, with no need to measure the child. It assumes adult height is strongly heritable, and calculates an average of the parents' heights, adjusted by a 13 cm constant reflecting the average height gap between adult men and women (boys adjusted upward, girls downward, before dividing by two to get the mid-parental height adjusted for the child's sex). This formula remains a statistical estimate, not an exact prediction: the associated 95% confidence interval is ±8.5 cm, meaning the child's real adult height has a 95% chance of falling within this fairly wide range around the calculated central value — an uncertainty that reflects the influence of many other factors on growth (nutrition, overall health during childhood, genetic factors specific to the child beyond the simple parental average). For a child over 4 years old, a more precise method (Khamis-Roche) exists, which additionally factors in the child's current height and weight, but requires those recent measurements; the Tanner method remains the best starting point without that data, or for a very young child. For the child's BMI once their current height and weight are known, see our BMI calculator.
Example: a boy, 180 cm father, 165 cm mother
Inputs
Father's height: 180 cm. Mother's height: 165 cm. Child's sex: boy.
Calculation
Estimated height = (180 + 165 + 13) ÷ 2 = 358 ÷ 2 = 179 cm, with a 95% confidence interval of 170.5 to 187.5 cm.
Result
This boy's adult height is estimated at 179 cm, with a realistic range of 170.5 to 187.5 cm.
Frequently asked questions
Why is this estimate's range so wide (±8.5 cm)?
Because adult height, while strongly heritable, also depends on many other factors specific to the child: their own genetic makeup (beyond just the parental average), nutrition during childhood and adolescence, overall health, and other influences still poorly understood individually. This ±8.5 cm range honestly reflects this real statistical uncertainty, rather than presenting a single figure as a certainty it isn't.
Does this formula work as well for a very young child as for a teenager?
The mid-parental method has the advantage of requiring no measurement of the child at all, making it usable from birth, unlike more precise methods (like Khamis-Roche) that require a recent height and weight measurement of the child from age 4 onward. For an older child with recent measurements available, a method incorporating that personal data generally gives a more precise estimate than the parental average alone.
What if a child's real height differs a lot from this estimate?
An isolated deviation from this statistical estimate isn't necessarily concerning, given the method's wide margin of uncertainty. On the other hand, tracking a child's growth curve over time (not just a one-off estimate) remains the reference tool for a pediatrician: a clear break in that growth curve warrants a medical opinion, far more than a deviation from a single mid-parental estimate.