Child Height Predictor Calculator
Estimate how tall a child will be as an adult. The main prediction uses the mid-parental method — the genetic average of both parents’ heights — which works at any age. For children roughly 4 to 17, entering the child’s current height and weight adds a Khamis-Roche refinement. Predictions carry a margin of about ±2 in.
For US units, enter heights in total inches (5 ft = 60 in, 6 ft = 72 in).
How height prediction works
A child’s adult height is set mostly by genetics — studies attribute roughly 60–80% of the variation to inherited factors — with nutrition, sleep, and health filling in the rest. The simplest reliable estimate is the mid-parental method: average the two parents’ heights and nudge up for a boy or down for a girl. The Khamis-Roche method improves on that for school-age children by folding in the child’s own current height and weight, which reflect how far along their growth already is. Neither predicts an exact number; both give a most-likely value with a margin around it.
How it’s calculated
Mid-parental (primary): take the average of the mother’s and father’s heights, then add 6.5 cm (about 2.5 in) for a boy or subtract 6.5 cm for a girl. This works at any age because it uses only the parents. Khamis-Roche (refinement): predicted adult height (in) = B₀ + b₁×(child height) + b₂×(child weight) + b₃×(mid-parent height), with age- and sex-specific coefficients from Khamis & Roche (1994, Pediatrics). We apply the published coefficients for boys ages 4–15, interpolating between age points; the mid-parental estimate is shown for every child. Results carry a standard error of about ±2 in (girls ±1.7 in, boys ±2.2 in).
This is an educational estimate, not medical advice, and does not account for growth disorders, unusual puberty timing, or ethnicity-specific patterns. Discuss any concern about a child’s growth with a pediatrician; a bone-age assessment gives a more precise prediction.
Worked example
A boy has a mother who is 5 ft 5 in (65 in) and a father who is 5 ft 10 in (70 in). The parental average is 67.5 in; adding 2.5 in for a boy gives a mid-parental prediction of 70 in — 5 ft 10 in, matching his father. If he is 10 years old, 55 in tall, and 77 lb, the Khamis-Roche refinement lands very close, about 70 in as well. The likely range is roughly 68–72 in.
Common mistakes
- Using remembered or estimated parent heights — a 1 in error on each parent shifts the prediction by about half an inch.
- Expecting a single exact number instead of a range; real children scatter around the estimate.
- Applying the Khamis-Roche refinement to a toddler; it is validated for roughly ages 4–17.
- Ignoring early or late puberty, which the parent-based method cannot see.
Where it is used
- Parents curious how tall a child may become.
- Pediatric well-child visits, as a sanity check against growth charts.
- Youth sports, weighing likely adult size for a position.
- Flagging growth that falls far from the genetic expectation for follow-up.
Frequently asked questions
How accurate is a child height prediction?
No non-invasive method is exact. The mid-parental method typically lands within about ±4 in (±10 cm), and the Khamis-Roche method, which also uses the child’s current height and weight, within roughly ±2 in (±4–6 cm). Predictions tighten as a child ages. Bone-age X-rays are more accurate but require a clinic visit.
What is the mid-parental height method?
It averages the two parents’ heights and adjusts for sex: for a boy, add about 6.5 cm (2.5 in) to the average; for a girl, subtract about 6.5 cm. This captures the genetic component of height, which accounts for an estimated 60–80% of the variation. It works at any age, including for infants.
What is the Khamis-Roche method?
Published by Khamis and Roche in 1994, it predicts adult height from the child’s current height and weight plus mid-parental height, using age- and sex-specific regression coefficients. It is one of the most accurate methods that does not need a bone-age X-ray. This tool applies it for boys ages 4–15; the mid-parental estimate is shown for everyone.
What age can I use this for?
The mid-parental estimate works at any age, even for babies, because it uses only the parents’ heights. The Khamis-Roche refinement is validated for children roughly 4 to 17 years old, since it relies on the child’s own measurements and remaining growth.
Can I make my child taller than predicted?
Genetics set most of the range, but nutrition, sleep, and general health help a child reach their potential. Chronic undernutrition or illness can hold height below the prediction. Extreme deviations from the mid-parental estimate can be a reason to talk with a pediatrician.