Child’s Adult Height Predictor (mid-parental)

Understanding the child's adult height predictor — concept and principle

This calculator estimates a child's adult height from the heights of both parents, a value called the mid-parental or target height. Paediatricians use it to judge whether a child's growth fits the family pattern, and parents use it out of curiosity. It is the simplest prediction method because it needs no X-ray or growth record.

The green band shows the ±8.5 cm range where most boys of these parents end up.

How it is calculated

Using the father's height F and mother's height M in cm (Tanner's method):

Boys: (F + M + 13) ÷ 2
Girls: (F + M − 13) ÷ 2
Target range: prediction ± 8.5 cm

The 13 cm is the average difference between adult men and women in the original reference data. Adding it to the mother's height converts her to a "male equivalent" for a son; subtracting it converts the father to a "female equivalent" for a daughter.

The principle

Adult height is strongly inherited, so the average of the parents, adjusted for sex, is a reasonable centre for the child's expected height. Children do not simply copy that average, though. Many genes, nutrition, illness and the timing of puberty all play a part, and very tall or very short parents tend to have children slightly closer to the population average, a pattern known as regression toward the mean. The ±8.5 cm band reflects this spread: about 95% of children reach an adult height inside it.

Worked example

Inputs: boy, father 175 cm, mother 162 cm.
Sum with the sex adjustment: 175 + 162 + 13 = 350.
Divide by 2: 175 cm predicted adult height.
Target range: 175 − 8.5 = 166.5 and 175 + 8.5 = 183.5, so 166.5 – 183.5 cm.
For a girl with the same parents: (175 + 162 − 13) ÷ 2 = 162 cm.

Each point is the calculator re-run with only “Father’s height (cm)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Father’s height (cm)	Predicted adult height
43.8	109.38
87.5	131.25
131	153.13
175	175
219	196.88
262	218.75
350	262.5

How to read the result

The prediction is the centre of a wide, roughly 17 cm band. If a child's height on a growth chart tracks a percentile that leads well outside the target range, or crosses percentile lines over time, that pattern is worth discussing with a paediatrician. More precise methods use bone age from a hand X-ray together with the child's current height.

Common mistakes

Using self-reported parental heights, which are often rounded up; measured values work better.
Reading the single number as a guarantee rather than the middle of a range.
Assuming that extra supplements or treatments will move a healthy child far beyond the family target.

Keep in mind: Mid-parental height is a screening estimate. It does not account for health conditions, early or late puberty, or nutrition, and it is not a diagnosis. Concerns about growth should be assessed by a paediatrician.

Frequently asked questions

How accurate is the mid-parental method?

It gives the right neighbourhood, but individual children can differ from the centre by several centimetres in either direction.

Can my child grow taller than both parents?

Yes. The range extends 8.5 cm above the prediction, and better nutrition across generations also adds height.

When does growth usually stop?

Typically a few years after puberty starts, often around 14–16 in girls and 16–18 in boys, once the growth plates close.

Sources: Tanner JM, Goldstein H, Whitehouse RH. Standards for children's height at ages 2–9 years allowing for height of parents. Arch Dis Child 1970;45:755–762

Checked 8 Nov 2026. Published formulas cited on the page. For information only — not medical advice.

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