Child height predictor: mid-parental height with its real range

Expected adult height range for a boy, from parents of 165 cm and 180 cmworked example

170.5 cm - 187.5 cm

Mid-parental estimate (the midpoint): 179 cm+/- 8.5 cm
Width of the band: 17 cmthe 3rd to 97th centile, per Tanner 1970
Sex adjustment used: +13 cm to the mother

The range is the answer here, not the midpoint. Tanner, who published the method, put the 3rd to 97th centile of expected adult height at plus or minus 8.5 cm around the estimate, and later work widened it further. Two parents’ heights simply do not determine a child’s adult height more precisely than that.

Realistic range

170.5 cm to 187.5 cm

Tanner's band of +/- 8.5 cm around the estimate spans the 3rd to 97th centile of expected adult height, so the honest answer is a 17 cm range. Later work widened the band further, to about +/- 9 cm for girls and +/- 10 cm for boys. The estimate also assumes a population like the one it was derived from and takes no account of the child's own measured growth, nutrition or health.

Mother’s height (cm)Adult height in centimetres.Father’s height (cm)Measured heights beat remembered ones, by a surprising margin.

Which form of the formula?

The 13 cm is the average adult height difference between the sexes in the populations Tanner worked with.

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Both forms of the formula, for the heights entered
Child	Midpoint estimate	Range (3rd-97th centile)
Boy	179 cm	170.5 cm - 187.5 cm
Girl	166 cm	157.5 cm - 174.5 cm

Tanner, Goldstein and Whitehouse, Archives of Disease in Childhood 1970. The band spans the 3rd to 97th centile of expected adult height; later work widened it to about 9 cm for girls and 10 cm for boys, so this is the narrowest defensible version.

What this does not know. It has never seen the child. It takes no account of their own measured growth, their nutrition, their health, or the timing of puberty, and it assumes a population like the one the method was derived from. A growth curve plotted across several visits tells a clinician far more than this arithmetic can.

The sources this defers to

NHS: your baby’s weight and height — how centile charts are actually read, and why crossing lines matters more than a single point

A measured child against a reference chart says much more than two parents’ heights do - see the growth percentile calculator.

A child height predictor applies Tanner's mid-parental method: add 13 centimetres to the mother's height for a boy, or subtract it from the father's for a girl, then average the two. The answer comes with Tanner's own band of plus or minus 8.5 centimetres, which spans the 3rd to 97th centile.

Mid-parental (target) height — boys: ((mother + 13) + father) / 2 cm; girls: ((father - 13) + mother) / 2 cm. Verified 2026-07-30 against Tanner, Goldstein and Whitehouse, Arch Dis Child 1970 (Tanner's band of +/- 8.5 cm around the estimate spans the 3rd to 97th centile of expected adult height, so the honest answer is a 17 cm range. Later work widened the band further, to about +/- 9 cm for girls and +/- 10 cm for boys. The estimate also assumes a population like the one it was derived from and takes no account of the child's own measured growth, nutrition or health.)

Everything you type here is computed in your browser. Nothing you enter is stored on a server, sent anywhere, or shared — there is no account and no health data to leak.

Frequently asked questions

How do you estimate a child's adult height from parents?

Tanner's mid-parental method: for a boy, add 13 cm to the mother's height and average that with the father's; for a girl, subtract 13 cm from the father's height and average that with the mother's. The 13 cm is the average adult height difference between the sexes.

How accurate is a mid-parental height estimate?

Tanner put the 3rd to 97th centile of expected adult height at plus or minus 8.5 cm around the estimate - a 17 cm range. Later work widened it further, to about 9 cm for girls and 10 cm for boys. A single predicted number, without that band, is misleading.

Does the child's own height matter more than the parents'?

Yes, over time. Mid-parental height says what the genetics point at; a child's own growth curve plotted across several visits shows what is actually happening. A paediatrician reads the two together, which is why this page links to the growth-centile tool rather than stopping here.

Why does the estimate use a 13 cm difference?

It is the mean adult height difference between men and women in the populations Tanner worked with. Adding it to the mother's height for a boy is the same arithmetic as taking the mid-parental average and adding 6.5 cm, which is how the method is sometimes written.

Can this tell me whether my child is growing well?

No. It takes two adult heights and does one piece of arithmetic; it never sees the child. Questions about growth belong with a clinician who can plot measurements over time against a reference chart and look at the pattern rather than a point.

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The next number

No body metric means much on its own. Here is what this one feeds into.

Growth percentile calculatorA measured child against a reference chart tells you far more than two parents' heights do.

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