Child Height Predictor Calculator
Estimate how tall your child will be as an adult. This calculator offers two methods. The Khamis-Roche method (ages 4 to 17) combines the child’s current height, current weight, and the parents’ heights into a regression equation, and is one of the most accurate non-invasive predictors available, with a standard error of about ±5 cm for boys and ±4 cm for girls. The simpler mid-parental (Tanner) formula uses only the parents’ heights and works for any age, including before birth, but has a wider 95% range of about ±8.5 cm.
↳10 years old
How We Calculate This
Two methods are available. Khamis-Roche (Khamis & Roche, Pediatrics 1994;94:504-507, with 1995 erratum) is a sex- and age-specific linear regression: predicted adult stature = B0 + b1·child_height + b2·child_weight + b3·midparent_height, applied at each half-year step from age 4.0 to 17.5. Coefficients in this calculator are a smooth approximation calibrated to published anchor values; predictions agree with established Khamis-Roche calculators to within roughly 1-2 cm. Mid-parental height uses the Tanner formula: (mother + father ± 13 cm)/2, with a 95% confidence band of ±8.5 cm.
Frequently Asked Questions
Which method is more accurate, Khamis-Roche or mid-parental?
Khamis-Roche is substantially more accurate. Its standard error is around 5 cm (2 in) for boys and 4 cm (1.7 in) for girls, compared to roughly 8.5 cm (3.3 in) for the simple mid-parental formula. Khamis-Roche works because it uses the child’s actual growth trajectory — current height and weight — in addition to genetics, while mid-parental relies only on parental heights.
Why does the Khamis-Roche method only work between ages 4 and 17?
The published Khamis-Roche regression coefficients (from the Fels Longitudinal Study) cover ages 4.0 through 17.5 in half-year steps. Below age 4 a child’s growth trajectory is still too variable for the regression to be reliable, and above 17.5 nearly all children have already reached their adult height. For ages outside this range, switch to the mid-parental mode.
How is mid-parental height calculated?
Mid-parental height (also called Tanner target height) is the average of the parents’ heights, adjusted for the child’s sex. For boys: add 13 cm (5 in) to that average. For girls: subtract 13 cm (5 in). This 13 cm offset is roughly the average adult height difference between men and women.
My prediction seems different from what I expected. Why?
Height prediction is an estimate, not a guarantee. Individual children can land several centimetres above or below their predicted value because of nutrition, health, late puberty, ethnicity, and many other factors. The low and high estimates shown are a 95% confidence range — about 19 of every 20 children fall inside this window.
Can I use this to predict the height of an unborn baby?
Yes, but only with the mid-parental method, since Khamis-Roche needs the child’s current height and weight. Mid-parental height gives a reasonable starting expectation — keep in mind the ±8.5 cm 95% range still applies, so the eventual adult height can vary considerably.
Related Calculators
You might also find these calculators helpful: Child Growth Percentile Calculator, and BMI Calculator.
This calculator provides estimates for educational purposes only. Results vary based on individual factors. Consult a healthcare professional for personalized advice.