Adult Height Predictor

How this is calculated

The "parents' heights" method uses the classic mid-parental height formula: average the two parents' heights, then adjust by about 6.5 cm (roughly 2.5 inches) up for boys or down for girls, since males and females differ in typical adult height on average. This gives a single midpoint estimate, plus a range of roughly ±8.5 cm to reflect that genetics from two parents can combine in a wide variety of ways in any individual child.

The "toddler doubling rule" is an older, simpler rule of thumb: it estimates adult height as roughly double a child's height at around age 2 for boys, or around 18 months for girls, since growth patterns suggest children have typically reached close to half their eventual adult height by that point. This calculator applies a similar ±9 cm range around that doubled figure.

Both methods are simplified statistical approximations, not clinical growth assessments — a pediatrician predicting height more precisely would use serial measurements plotted on a growth curve over time, and sometimes a bone-age X-ray, rather than a single formula.

The wider range shown alongside the midpoint estimate isn't a margin of error in the statistical sense so much as an honest acknowledgment that any formula based on just one or two data points can only narrow down the realistic possibilities, not pinpoint an exact future height.

Common edge cases & things to know

Puberty timing has a real effect on when a child reaches their adult height, but the formulas above don't account for it directly. Children who enter puberty earlier tend to reach their adult height sooner (sometimes with a shorter overall growth window), while later-developing children often keep growing for longer — both patterns can still land within a normal adult height range.

These formulas are population averages drawn largely from broad historical datasets; they don't factor in ethnicity-specific growth patterns, chronic health conditions, nutrition, or unusually short or tall parents, all of which can shift an individual child's actual outcome outside the estimated range.

A single measurement is far less informative than tracking growth over time. Our Baby Growth Percentile Calculator can help you see how your child's height is tracking against their own curve across multiple checkups, which is generally a more meaningful signal than either formula here.

Sources

Mid-parental height methodology and growth-tracking guidance referenced from the American Academy of Pediatrics (AAP), HealthyChildren.org, and the CDC's pediatric growth chart program. If you have specific concerns about your child's growth trajectory, a pediatrician is the right resource, not a formula.