Height Calculator (Adult Height Predictor)

A child's adult height is influenced by genetics (60–80%) and environmental factors like nutrition, sleep, and overall health. This calculator uses two methods — the Khamis-Roche formula (for children aged 2–17) and the mid-parental height formula — to give a scientifically grounded estimate. Results typically have a margin of error of about 2 inches.

The mid-parental height formula averages both parents' heights and adjusts for the child's sex. For boys: (mother's height + father's height) / 2 + 2.5 inches. For girls: (mother's height + father's height) / 2 − 2.5 inches. This gives a rough genetic target height based on parental stature alone.

The Khamis-Roche method is a regression-based statistical approach that uses the child's current age, height, weight, and the average of both parents' heights to predict adult stature. It is considered one of the most accurate non-bone-age methods available for children aged 4 and older, with a standard deviation of about 2.1 inches for boys and 1.7 inches for girls.

Girls typically reach their full adult height around age 14–15, usually within 1–2 years after their first menstrual period. Most girls experience their peak growth spurt between ages 10 and 13. After puberty, very little additional height gain occurs.

Boys generally stop growing around ages 16–18, though some may continue adding small amounts of height into their early 20s. The male growth spurt typically peaks between ages 12 and 15, later than girls on average.

While genetics set the ceiling, ensuring proper nutrition (especially adequate protein, calcium, and vitamin D), sufficient sleep, and regular physical activity can help a child reach their genetic height potential. Hormonal imbalances or underlying medical conditions can also affect growth and should be evaluated by a pediatrician if there is concern.

No height prediction method is perfectly accurate. The Khamis-Roche method has a standard error of roughly 2 inches, meaning the actual adult height will typically fall within about 2 inches of the predicted value. Factors like nutrition, illness, and hormonal health can all influence final height.

Yes, even identical twins can differ slightly in height despite sharing the same DNA. Environmental factors during development — such as differences in nutrition, illness, stress, or birth conditions — can cause height differences of up to a few inches, illustrating that genes are not the sole determinant of height.