Child Height Predictor: Predicted Adult Height Calculator
The mid-parental height method is the simplest and most widely used statistical approach for estimating a child's adult height. Developed from research by Tanner and colleagues, the method uses the average of both parents' heights and adjusts for the child's sex by adding 5 inches for boys (reflecting the average male-female height difference) or subtracting 5 inches for girls. The resulting mid-parental height is the statistical centre of the predicted range, with roughly two-thirds of children falling within 2 inches above or below the prediction. The method reflects the strong genetic component of height: parental stature is the single biggest predictor of adult height for most children. However, it is a population-level average and does not account for every individual factor. Nutrition, sleep, chronic illness, hormone levels, and the timing of puberty all influence final adult height in ways that parental height alone cannot capture. The Khamis-Roche method adds the child's current age, height, and weight for a more refined estimate, and bone-age X-rays are used for clinical assessments. This calculator supports both metric and imperial units and shows the predicted height with its expected range. The result is for informational purposes only and is not a medical assessment of growth or health.
Predicted adult height: -- (range: --).
How the mid-parental height formula works
The formula is applied in inches regardless of which unit system you choose. The calculator converts metric inputs to inches, applies the formula, and converts back.
Boys (inches): Predicted = (Father_in + Mother_in + 5) / 2
Girls (inches): Predicted = (Father_in + Mother_in - 5) / 2
Range: Predicted height +/- 2 inches
Metric conversion: 1 inch = 2.54 cm
Worked example (imperial)
Father 5 ft 10 in (70 in), mother 5 ft 4 in (64 in), boy:
- (70 + 64 + 5) / 2 = 139 / 2 = 69.5 in
- Convert: 69 in = 5 ft 9 in, 0.5 in remainder = 5 ft 9.5 in
- Range: 5 ft 7.5 in to 5 ft 11.5 in
About the Khamis-Roche method
The Khamis-Roche method (published in Pediatrics, 1994) extends the mid-parental height approach by also factoring in the child's current age, height, and weight. It provides somewhat more accurate predictions, particularly as children approach puberty. If you want to use the Khamis-Roche method, you will need the child's current measurements and can consult the CDC growth charts to track percentile trajectory alongside the prediction.
Factors that influence adult height beyond genetics
| Factor | Effect on height |
|---|---|
| Nutrition | Adequate protein, calcium, vitamins D and K support bone growth; chronic malnutrition can reduce final height |
| Sleep | Growth hormone is primarily secreted during deep sleep; poor sleep in childhood may reduce growth |
| Physical activity | Regular moderate exercise supports healthy growth; excessive endurance training before puberty may slightly delay maturation |
| Chronic illness | Conditions affecting absorption (coeliac disease, inflammatory bowel disease) or hormone production can impair growth |
| Puberty timing | Early puberty brings a growth spurt sooner but may reduce total growth duration; late puberty extends it |
When to consult a paediatrician
If your child's measured height is consistently below the 3rd percentile on CDC growth charts, or if their growth rate slows significantly between measurements, a paediatrician or paediatric endocrinologist can investigate potential causes. These may include growth hormone deficiency, thyroid disorders, coeliac disease, or other conditions that respond to treatment. Early identification leads to better outcomes.
Growth charts from the CDC are available at cdc.gov/growthcharts and provide percentile curves for height, weight, and BMI from birth through age 20.
Child height predictor: frequently asked questions
How accurate is the mid-parental height method?
The mid-parental height method gives a statistical estimate based on parental heights. Research by Tanner and colleagues found that about 95% of children reach an adult height within approximately 4 inches (10 cm) of the mid-parental prediction, meaning the range of plus or minus 2 inches captures roughly two-thirds of children. Environmental factors such as nutrition, health, physical activity, and sleep quality during childhood significantly influence final adult height. The prediction becomes more reliable as a child approaches puberty.
What is the mid-parental height formula?
For boys: predicted height (inches) = (father's height in inches + mother's height in inches + 5) divided by 2. For girls: predicted height (inches) = (father's height in inches + mother's height in inches minus 5) divided by 2. The 5-inch adjustment accounts for the average height difference between adult males and females. The result is typically reported with a range of plus or minus 2 inches to reflect natural variation.
Are there more accurate methods for predicting adult height?
The Khamis-Roche method (1994), published in Pediatrics, adds the child's current age, height, and weight to the parental height calculation and provides somewhat more precise predictions, particularly closer to puberty. The bone age method, which uses an X-ray of the left hand and wrist to assess skeletal maturity, is used by paediatric endocrinologists for clinical assessments. CDC growth charts can also be used to track a child's height trajectory relative to peers.
Does the prediction work the same for early and late developers?
No. Children who go through puberty earlier tend to reach their adult height sooner but may not grow as tall overall. Late developers may continue growing longer and sometimes exceed mid-parental predictions. Puberty timing is influenced by genetics, nutrition, and other factors. If a child's growth trajectory deviates significantly from predictions or CDC growth chart percentiles, a paediatric endocrinologist can assess whether further evaluation is warranted.
Can I use this calculator if I know my child's height in metric only?
Yes. Select the metric option. The calculator converts parent heights from centimetres to inches internally (dividing by 2.54), applies the formula, and converts the result back to centimetres for display. The predicted height and range are shown in the units you selected. The underlying formula always operates in inches because that is the unit in which the original research equation was defined.
Official sources
- Tanner JM, Goldstein H, Whitehouse RH. Standards for children's height at ages 2-9 years allowing for heights of parents. Archives of Disease in Childhood. 1970;45(244):755-762.
- CDC Growth Charts: Clinical Growth Charts.
- Khamis HJ, Roche AF. Predicting adult stature without using skeletal age: the Khamis-Roche method. Pediatrics. 1994;94(4 Pt 1):504-507.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology. General information only, not medical advice.