Child height predictor
Enter the child's sex and the heights of the mother and father. The calculator averages the parents' heights, adjusts for the child's sex and shows a likely range. It is a rough estimate based on genetics alone, not a promise.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose metric or US units and whether the child is a boy or a girl.
- Enter the father’s and the mother’s height.
- Read the predicted adult height and the likely range.
The mid-parental height method, associated with J. M. Tanner:
- boy: (father + mother + 13 cm) ÷ 2
- girl: (father + mother − 13 cm) ÷ 2
and the likely range is the prediction ± 8.5 cm. In inches the calculator converts the parents’ heights to centimetres first (1 in = 2.54 cm) and converts the result back.
Worked example
Father 180 cm, mother 165 cm. For a boy: (180 + 165 + 13) ÷ 2 = 179 cm, range 170.5 to 187.5 cm. For a girl: (180 + 165 − 13) ÷ 2 = 166 cm, range 157.5 to 174.5 cm.
Limits
- It is a rough estimate from genetics only. Diet, illness, medicines and the timing of puberty can all change adult height.
- The predictions are averages for a population. The prediction tends to pull towards the middle, so children of very tall or very short parents may differ more.
- This is general information, not medical advice. If you are concerned about a child’s growth, ask a paediatrician.
Frequently asked questions
How accurate is the mid-parental height method?
It is a rough guide. The method itself quotes a margin of about 8.5 cm (3.3 in) either side of the prediction, so the range is wide. Nutrition, health, puberty timing and chance all play a part, and many children end up outside the range.
Why add or subtract 13 cm?
Men are on average about 13 cm (5 in) taller than women. Adding 13 cm to the parents' combined average for a boy, or subtracting it for a girl, puts the parents' heights on the child's own sex scale.
Can I use this for a child who is still growing?
Yes, it does not need the child's current height or age. A paediatrician combines the child's measurements on a growth chart, sometimes with a bone-age X-ray, for a much better prediction.
Does it work if the parents are of very different heights or one is not the biological parent?
It assumes both are biological parents. With a large difference between the parents the child's height can land anywhere in the range or beyond. It is not meant for children with growth disorders.
Should I worry if my child is below the predicted height?
Not on the basis of this tool. If you are concerned about growth, a doctor can plot your child's height over time; falling away from their growth curve is more informative than any single prediction.