Child Height Predictor

What exact formula does this tool use?

It uses the mid-parental height method in centimetres. For a boy the prediction is (father’s height + mother’s height + 13) ÷ 2, and for a girl it is (father’s height + mother’s height − 13) ÷ 2. With a 178 cm father and a 165 cm mother, a boy comes out at 178.0 cm and a girl at 165.0 cm. The result is printed in centimetres and in feet and inches.

How reliable is the prediction?

It is a rough statistical estimate based only on the two parents’ heights, and individual children vary widely around it. It does not account for nutrition, health conditions, the timing of puberty or anything else about your child, and it is not a medical assessment. If you are concerned about a child’s growth, talk to a pediatrician.

What is the plus or minus 5 cm range?

It is a fixed band of 5 cm either side of the prediction, so a 178.0 cm prediction is shown as 173.0–183.0 cm. The tool applies the band mechanically; it is not calculated from data about your family. A child can finish taller or shorter than the band, so do not read the edges as limits.

How does the optional current height comparison work?

If you enter a current height and an age of 2 or more and under 18, the tool rounds the age to the nearest whole year and looks up a median height for that age and sex in a table built into the code. It reports whether your child is within 2 cm of that figure or how many centimetres above or below it. A 10-year-old girl measuring 140 cm is shown as 2.0 cm above the built-in median of 138 cm.

Does the current height change the prediction?

No. The predicted adult height and range depend only on the parents’ heights and the child’s sex. The comparison line is separate, and it is not a percentile or a growth-chart reading. The built-in medians are approximate reference values and should not be used to judge growth.

What happens if I clear a parent’s height or enter zero?

The tool shows an Input needed message instead of a number, and a cleared box counts as zero. Negative values are treated as zero, so they trigger the same message. Beyond requiring positive numbers, it does not check that the heights are plausible, so a typo such as 17 instead of 170 will produce a nonsense prediction.

How are feet and inches calculated?

The centimetre value is divided by 2.54 and rounded to the nearest whole inch, then split into feet and inches. A 170.5 cm prediction therefore displays as 5 ft 7 in. The rounding applies to the range endpoints too, so converted values can look slightly different from the centimetre figures.

Does the method work for adopted children or half-siblings?

The method is built on the heights of the child’s biological parents, so the figure only means something when those are the heights you enter. Entering the heights of adoptive parents tells you nothing about the child’s genetic height. The tool has no way of knowing which situation applies.