Adult Height Predictor
Estimate a child's likely adult height from the parents using the Tanner mid-parental method, with a 95% range so you can see how much the prediction varies.
Predicted adult height (cm)
178
- Mid-parental height (cm)
- 171.5
- 95% range — lower estimate (cm)
- 169.5
- 95% range — upper estimate (cm)
- 186.5
- Method
- Tanner mid-parental (±8.5 cm)
The Tanner mid-parental height method averages the parents' heights and shifts by half the adult sex difference: +6.5 cm for boys, −6.5 cm for girls. Around 95% of children land within roughly ±8.5 cm of that estimate; outliers are normal and most children sit somewhere in the band. This is a population-level prediction, not a medical assessment — for individual growth concerns, see a paediatrician.
How to use this calculator
Pick your units, choose whether the child is a boy or a girl, and enter both parents' heights. The calculator returns the predicted adult height, the underlying mid-parental height it was derived from, and a 95% prediction range so you can see how much real children can vary around the central estimate. If one parent's height is unknown, the standard practical workaround is to use the average adult height for that parent's population; results then become noticeably less precise.
How the calculation works
The Tanner mid-parental height (MPH) method, published by Tanner, Goldstein and Whitehouse in Archives of Disease in Childhood (1970), takes the average of the two parents' heights and adjusts by half the mean adult sex difference of about 13 cm. In one form: boy = (father + mother + 13 cm) / 2; girl = (father + mother − 13 cm) / 2. Equivalently, boys are predicted at MPH + 6.5 cm and girls at MPH − 6.5 cm. Tanner reported that roughly 95% of children land within about ±8.5 cm of this estimate, which is the band this calculator shows.
Worked example
Father 178 cm, mother 165 cm, boy. Mid-parental height = (178 + 165) / 2 = 171.5 cm. Predicted adult height = 171.5 + 6.5 = 178 cm. The 95% range is roughly 169.5–186.5 cm, so a final adult height anywhere in that band would be unremarkable. For a girl with the same parents, the prediction shifts to 171.5 − 6.5 = 165 cm with the same ±8.5 cm spread.
Frequently asked questions
How accurate is predicting a child's adult height from the parents?
The Tanner mid-parental method is a population-level estimate, not a precise prediction for an individual. Tanner's original 1970 paper reported a 95% range of roughly ±8.5 cm (about ±3.3 inches) around the central estimate. Most children land somewhere in that band, but nutrition, puberty timing, illness, and genetics outside the parents' own height all shift the outcome. Treat the number as a midpoint of a wide range, not a target.
What is the formula?
Tanner mid-parental height uses two equivalent forms. The shorter one: take the average of the parents' heights, then add 6.5 cm for a boy or subtract 6.5 cm for a girl. The longer one: boy = (father + mother + 13 cm) / 2; girl = (father + mother − 13 cm) / 2. The 13 cm constant captures the average adult height difference between men and women. Both forms give exactly the same answer.
What if I only know one parent's height?
The method needs both. The usual workaround is to substitute the average adult height for that parent's population — about 175 cm for adult men and 162 cm for adult women globally, with local figures available from your country's statistics office. The prediction gets noticeably less precise because half of the information is being averaged away, so widen the uncertainty band in your head when you use that shortcut.
Does it work for very tall or very short parents?
It does, with one caveat: predictions regress toward the mean. The children of two very tall parents tend to be tall but slightly shorter than the mid-parental estimate; the children of two very short parents tend to be slightly taller. The Tanner formula does not encode this regression explicitly, so for parents at the extremes the central estimate is biased outward and the real adult height is more likely to fall on the inner side of the predicted range.
Is this medical advice?
No. This calculator returns a statistical estimate based on a 1970 paediatric method and is for general interest only. It cannot diagnose growth disorders, predict puberty, or substitute for clinical evaluation. If you are worried about a child's height velocity, very early or very late puberty, or a height that is consistently outside the 3rd or 97th centiles on a growth chart, talk to a paediatrician — they have access to growth-chart data, bone-age imaging, and clinical tests this calculator cannot replicate.
Why is there a 13 cm difference between boys and girls?
The 13 cm (about 5 inches) comes from the average difference in adult height between men and women across populations Tanner used in 1970. Modern data still puts the gap at roughly 12 to 14 cm in most countries, so the original constant remains a reasonable approximation. If you are working with a population where the sex gap is materially different, the predicted point shifts but the ±8.5 cm uncertainty band is wide enough that the impact on any individual estimate is small.