Child Height Predictor
Estimate how tall your child may be as an adult from both parents' heights using the mid-parental (target height) method, with the usual ±8.5 cm range, plus the traditional doubling rule from height at age 2. Calculated privately in your browser.
A statistical estimate based on parents' heights only. About 95% of children end up within the range shown. Concerns about growth are best checked by a pediatrician.
How to use the Child Height Predictor
- Choose units (cm or ft/in) and whether the child is a boy or a girl.
- Enter the biological father's and mother's heights, measured without shoes if possible.
- Optionally enter the child's height at 2 years (boys) or 18 months (girls) for the doubling estimate.
- Press Predict adult height to see the target height, the likely range and the chart.
The mid-parental height formula
The mid-parental or "target height" method (Tanner and colleagues, 1970) assumes a child is likely to grow to the average of the parents' heights, adjusted for the roughly 13 cm (5 in) difference between average adult men and women:
| Child | Metric | Imperial |
|---|---|---|
| Boy | (father + mother + 13 cm) ÷ 2 | (father + mother + 5 in) ÷ 2 |
| Girl | (father + mother − 13 cm) ÷ 2 | (father + mother − 5 in) ÷ 2 |
| Likely range | target ± 8.5 cm | target ± about 3.3 in |
Worked example: father 178 cm (5′10″) and mother 165 cm (5′5″). A son's target is (178 + 165 + 13) ÷ 2 = 178 cm (5′10″), with a likely range of 169.5–186.5 cm. A daughter's target is (178 + 165 − 13) ÷ 2 = 165 cm (5′5″), range 156.5–173.5 cm. The ±8.5 cm band corresponds to about two standard deviations, so roughly 95% of children fall inside it.
Other prediction methods
- Doubling rule. Boys are around half their adult height at 2 years, girls at about 18 months. Doubling that height is a quick folk estimate; it is included here as a second opinion only.
- Khamis-Roche method (Khamis and Roche, Pediatrics, 1994, with an erratum in 1995). It combines the child's current height and weight, age, sex and mid-parental height with coefficients that change for every half-year of age from 4 to 17.5. It was built on data from the Fels Longitudinal Study (white American children) and its accuracy is commonly quoted as within about 2 inches (5 cm) for most children. We have not included it, because it needs the published coefficient tables; ask your pediatrician or use the original paper.
- Bone age methods (Bayley-Pinneau, Tanner-Whitehouse) use a hand X-ray to judge skeletal maturity. They are the most precise clinical methods, especially for children who are maturing early or late, but they need a specialist.
What affects how tall a child grows
Genes explain most of the difference in adult height between people in the same population (heritability is often estimated at around 80%), but nutrition, chronic illness, sleep and the timing of puberty matter too. Children who are much shorter than their target height, who grow less than about 4–5 cm a year between age 4 and puberty, or who cross percentile lines on their growth chart should see a doctor. For babies and toddlers, compare measurements with the WHO standards in the baby percentile calculator.
Frequently asked questions
How accurate is the mid-parental height method?
It gives a target height that most children end up near, but about 95% of children reach an adult height within roughly ±8.5 cm (±3.3 in) of it. It does not account for the child's own growth so far, nutrition, health or puberty timing, so treat it as a rough guide.
What is the formula for mid-parental height?
For boys: (father's height + mother's height + 13 cm) ÷ 2. For girls: (father's height + mother's height − 13 cm) ÷ 2. In inches, add or subtract 5 inches instead of 13 cm. The 13 cm is the average difference in adult height between men and women.
Does doubling height at age 2 really work?
It is an old rule of thumb: boys reach roughly half their adult height at about 2 years and girls at about 18 months. It works surprisingly often but can be off by several centimetres either way, so it is shown only as a second rough estimate.
What is the Khamis-Roche method?
It is a more detailed prediction published by Khamis and Roche in Pediatrics in 1994 that uses the child's current height, weight, age and the parents' heights with age-specific coefficients. It was developed on white American children aged 4 to 17.5 and is commonly quoted as accurate to within about 2 inches. This tool does not include it; pediatricians and specialist calculators use the published coefficient tables.
Can my child grow taller than predicted?
Yes. Good nutrition, sleep and overall health help a child reach their genetic potential, and many children differ from the prediction. Very short or very tall predictions compared with the parents, or a child falling across growth percentiles, are reasons to see a pediatrician.
What if I only know one parent's height?
The method needs both biological parents. Using an average height for the unknown parent gives a much less reliable estimate, and adoptive parents' heights do not predict a child's height.