Height Calculator
Predict a child's adult height using two scientific methods, check height percentile, see growth milestones, and convert between cm, feet, and inches — all in one place.
The most accurate non-skeletal-age method. Requires child's current age, height, and weight, plus both parents' heights.
Works for any age — even for unborn babies or toddlers. Uses only parents' heights. Less precise than Khamis-Roche but widely used by paediatricians.
Convert instantly between centimetres, feet & inches, metres, and millimetres.
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Compare predicted or actual height against average heights from countries around the world. Data sourced from NCD Risk Factor Collaboration.
| Rank | Country | Avg. height | vs. your height | Visual |
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How does the Khamis-Roche height predictor work?
Developed by Dr. Harry Khamis and Dr. Alex Roche, this method uses the child's current age, height, weight, and both parents' heights to predict adult stature. It has a standard error of approximately 2.1 cm for boys and 1.7 cm for girls — significantly more accurate than methods using only parental height.
The prediction is based on regression equations developed from longitudinal growth study data. It is valid for children aged 4 to 17.5 years and should only be used as an estimate.
What is the mid-parental height formula?
The mid-parental formula is a quick estimate used widely in paediatric practice. For a boy: add both parents' heights in cm, add 13 cm, then divide by 2. For a girl: add both parents' heights in cm, subtract 13 cm, then divide by 2. The result has a typical range of ±10 cm.
This method works for any age — including newborns and toddlers — because it only relies on the parents' heights, not the child's current measurements.
When do boys and girls stop growing?
Girls typically reach their final adult height between ages 14–16, roughly 2–2.5 years after the onset of menstruation. Most girls have completed 98% of their growth by age 15.
Boys continue growing for longer, usually reaching full adult height between ages 16–18. Some boys may continue to grow slightly until age 21. Growth plates (epiphyseal plates) in the long bones fuse and stop producing new bone tissue at the end of puberty.
What factors affect a child's final height?
Genetics accounts for roughly 60–80% of adult height variation. The remaining 20–40% comes from environmental factors including nutrition (especially protein and micronutrient intake during growth spurts), quality of sleep (growth hormone is released during deep sleep), physical activity, chronic illnesses, and medications like long-term corticosteroids.
Children with consistently good nutrition, adequate sleep, and regular physical activity tend to reach the upper end of their genetic height range.
Frequently asked questions
How accurate is the height prediction?
The Khamis-Roche method has a standard error of ~2.1 cm for boys and ~1.7 cm for girls, meaning the real adult height typically falls within 4 cm of the prediction. The mid-parental formula is less precise, with a ±10 cm range. Both are estimates — no calculator can account for all genetic and environmental variables.
Can I use this for a child under 4 years old?
The Khamis-Roche method is validated only for children aged 4–17.5 years. For younger children, use the mid-parental formula instead, which works from birth onward and only requires the parents' heights.
What is a normal height percentile for a child?
Any percentile between the 3rd and 97th is considered within the normal range. A child at the 50th percentile is exactly average. Doctors look more closely if a child falls below the 3rd or above the 97th percentile, or if their percentile rank shifts significantly over time.
Does height skip a generation?
Height is polygenic — controlled by hundreds of genes. Because of this, tall grandparents can have average-height children who then have tall grandchildren again. It is not a simple skip, but rather statistical regression toward the population mean across generations.
How is height percentile calculated?
Height percentile compares an individual's height against a reference population of the same age and sex. A person at the 75th percentile is taller than 75% of people in that group. This calculator uses CDC/WHO adult reference data for the percentile estimates.
What is the average male and female height worldwide?
The global average height for adult men is approximately 171 cm (5 ft 7.3 in) and for adult women approximately 159 cm (5 ft 2.6 in), based on NCD Risk Factor Collaboration data. Averages vary significantly by country — the Netherlands has one of the tallest populations, while parts of South and Southeast Asia have lower averages.