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Child Height Calculator

Enter both parents' heights and the child's sex to get a predicted adult height range.

How tall will a child grow when neither parent is tall? Genetics accounts for most of adult height, and mid-parental height is the formula that turns the saying into a number, estimating genetic potential from the parents' heights. Enter both heights and the child's sex — boys and girls use a different calculation — and the result arrives with an upper and a lower bound.

On the conventions: the ±5 cm band covers most cases, but nutrition, sleep, activity and illness can push the actual height outside it, so the figure estimates genetic potential rather than promising anything; enter the parents' heights without shoes, and note that for a child who matured early this formula underestimates adult height.

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How to use

  1. Enter both parents' heights, without shoes.
  2. Select the child's sex.
  3. Read the predicted adult height and its ±5 cm band.
  4. Treat it as genetic potential, not a guarantee.

How it works

The genetic target-height formula

The genetic target height (FPH, mid-parental height) first converts both parents' heights to the same sex scale and averages: boys' target = (father + mother + 13) / 2, girls' = (father + mother - 13) / 2. The +13 comes from adult men averaging about 13 cm taller than women. For father 175 cm and mother 162 cm, a boy's target is 175 cm and a girl's 162 cm.

Understanding the +/-5 cm range

The result is a range, not a point: actual adult height falls within the target +/-5 cm for about 2/3 of people, so the tool gives both bounds. Falling outside is also common — pubertal timing, nutrition and illness all matter, and the target is a genetic-level expectation, not a promise.

What matters more than target height

What truly needs watching is the growth curve's trend, not any single height: growing steadily along a percentile is usually fine; if the percentiles keep sliding (say from the 50th to the 10th), or height is persistently below the 3rd percentile for the same age and sex, see a pediatric endocrinologist to assess bone age and growth-hormone markers. Sleep (9-11 hours school-age), adequate protein and calcium, and vertical-impulse exercise are the three controllable levers.

Calculation basis: the mid-parental (FPH) method — for boys (father + mother + 13) ÷ 2, for girls (father + mother − 13) ÷ 2, with a range of ±5 cm. It reflects genetic potential only (roughly two thirds of adult height variation) and is not a growth diagnosis.

Code example

JavaScript The FPH mid-parental height formula 

function targetHeight(fatherCm, motherCm, male) {
  const boy = (fatherCm + motherCm + 13) / 2;
  const girl = (fatherCm + motherCm - 13) / 2;
  const t = male ? boy : girl;
  return { target: t, range: (t - 5).toFixed(1) + "~" + (t + 5).toFixed(1) };
}

targetHeight(175, 162, true);   // target 175, range 170~180

Python The same formula in Python 

def target_height(father_cm, mother_cm, male):
    t = (father_cm + mother_cm + 13) / 2 if male \
        else (father_cm + mother_cm - 13) / 2
    return t, (t - 5, t + 5)

target_height(175, 162, True)   # (175.0, (170.0, 180.0))

FAQ

Is target height accurate?

It's a population-statistical prediction range: about 2/3 of people fall within +/-5 cm, and about 1/3 will exceed it. It reflects a genetic expectation and doesn't predict an individual's final height.

Why add 13 for boys?

Because adult men average about 13 cm taller than women. Converting the mother's height to the male scale and averaging with the father gives a boy's genetic expectation; for girls, subtract 13 accordingly.

My child is shorter than peers — can they reach the target?

The percentile trend is more telling. Growing steadily along a percentile is usually fine; if percentiles keep sliding, or stay below the 3rd percentile, evaluation is needed rather than waiting until puberty.

What post-birth factors help height?

Three matter most: ensure sleep (growth hormone is mainly secreted during deep sleep; 9-11 hours for school age), adequate protein and calcium, and more vertical-impulse exercise (jump rope, basketball). Also avoid obesity and early exposure to tobacco and alcohol.

What is bone age, and should it be measured?

Bone age assesses skeletal maturity via a wrist X-ray. A bone age below the actual age means growth potential remains; an advanced bone age (like precocious puberty) shortens the growth period. Combining target height with bone age predicts better, judged by a pediatric endocrinologist.

If both parents are short, is there no hope?

Genetics explains about 2/3 of height variation, leaving about 1/3 to post-birth factors; grandparental height also shows up. So the target is only a first-order approximation of parents' heights, not an upper limit.

Are parents' heights uploaded?

No. They're used only for local formula application, not sent or collected; the site has no account system linking to a specific family. If you saved history, records stay only in your browser and are clearable in one click.