Height Calculator: Predict a Child's Adult Height
Predict a child's adult height from the parents' heights by the mid-parental method, with its ±8.5 cm target range, plus the twice-the-height-at-age-2 rule. Enter cm or feet and inches. Nothing is uploaded.
Enter both parents' heights to predict the adult height.
The mid-parental method assumes a child grows along the family's height pattern; about 95% of children end up within 8.5 cm of it. The Khamis-Roche method is more accurate for children aged 4 to 17, but it needs the child's current height and weight and age-specific coefficient tables that are not used here.
About the Height Calculator
The Height Calculator predicts how tall a child is likely to be as an adult. It uses the mid-parental height method, which averages the parents' heights and adjusts for the child's sex, and gives a target range of 8.5 cm either side. If you know the child's height at age 2, it adds a second estimate from the old rule of thumb that a child is about half their adult height at that age.
Heights can be entered in centimetres or in feet and inches, and every result is shown in both.
This is an estimate, not medical advice. Height depends on nutrition, health, sleep and the timing of puberty as well as on genes, and many children end up taller or shorter than either method predicts. If you are worried about a child's growth, ask a doctor or health visitor to plot it on a growth chart.
How to predict adult height
Steps
- Choose Boy or Girl and the unit you want to use.
- Enter the father's and the mother's adult heights.
- Optionally, enter the child's height at 24 months for a boy or 18 months for a girl.
- Read the predicted adult height, the target range and the second estimate.
The mid-parental method
The method was set out by James Tanner and colleagues in 1970. Men are on average about 13 cm taller than women, so the method adds 13 cm to the parents' total for a boy and takes 13 cm away for a girl, then halves the result:
About 95% of children reach an adult height within 8.5 cm of this figure, which is the target range shown. Doctors use it to judge whether a child's growth fits the family pattern.
Twice the height at age 2
Children tend to reach about half their adult height by their second birthday. Girls grow faster early on, so for them the rule uses the height at 18 months. Doubling that early height gives a quick second estimate. It is a rule of thumb, not a published equation, and is less reliable than the mid-parental method.
Why not the Khamis-Roche method?
The Khamis-Roche method, published in 1994, is more accurate for children aged 4 to 17. It combines the child's current height and weight with the mid-parental height, using a different set of coefficients for every half-year of age and for each sex. Those coefficient tables are not used here, so this calculator offers the simpler methods only.
Worked example
A father of 180 cm and a mother of 165 cm have a son. His predicted adult height is (180 + 165 + 13) ÷ 2 = 179 cm, or 5 ft 10.5 in, with a target range of 170.5 cm to 187.5 cm. A daughter of the same parents is predicted to reach (180 + 165 − 13) ÷ 2 = 166 cm.
Privacy
Every calculation runs in your browser. Nothing is uploaded, and the heights you enter are never sent anywhere.
Related tools
Convert between centimetres and feet with the Length Converter, work out a child's exact age with the Age Calculator, or check weight for height with the BMI Calculator.
Sources
- Tanner, J. M., Goldstein, H., & Whitehouse, R. H. (1970). Standards for children's height at ages 2–9 years allowing for height of parents. Archives of Disease in Childhood, 45(244), 755–762.
- Khamis, H. J., & Roche, A. F. (1994). Predicting adult stature without using skeletal age: the Khamis-Roche method. Pediatrics, 94(4), 504–507.
Open-source credits
The calculations are implemented in-house in TypeScript, with no third-party libraries. They follow the published mid-parental (Tanner) height method with its ±8.5 cm target range, and the twice-the-height-at-age-2 rule of thumb.
Frequently asked questions
How accurate is the mid-parental height prediction?
About 95% of children reach an adult height within 8.5 cm of the mid-parental figure, which is the target range shown. It cannot account for nutrition, illness or the timing of puberty, so treat it as a guide to the family pattern rather than a firm forecast.
Why add or subtract 13 cm?
Adult men are on average about 13 cm taller than adult women. Adding 13 cm for a boy or taking 13 cm away for a girl puts both parents on the same scale as the child before their heights are averaged.
Is a child really half their adult height at age 2?
Roughly. Boys are close to half their adult height at 24 months, and girls, who grow faster early on, at about 18 months. Doubling that height is a quick rule of thumb, but it is less reliable than the mid-parental method.
What is the Khamis-Roche method?
Published in 1994, it predicts adult height for children aged 4 to 17 from the child's current height and weight and the parents' heights, using coefficient tables for each half-year of age and each sex. It is more accurate than the mid-parental method, but those tables are not used here.
When should I talk to a doctor about my child's height?
Ask a doctor if your child's growth seems to have slowed or sped up, if they are much shorter or taller than their classmates, or if their height is far outside the predicted range. A doctor can plot measurements over time on a growth chart, which says much more than a single prediction.