Child Height Predictor
Predict adult height from parents
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Child Height Predictor turns the numbers behind predicting adult height from parents into an instant, step-by-step result. You supply Father (cm) and Mother (cm) to Child Height Predictor; the answer follows at once. Child Height Predictor displays each intermediate figure as well. Child Height Predictor suits budgeting and planning checks. You can disconnect once Child Height Predictor has loaded; the arithmetic runs locally. Looking for child height predictor or free online child height predictor calculator? Child Height Predictor covers both. Child Height Predictor is great for comparing scenarios. Change one value and watch. Child Height Predictor is free, instant and local.
Child height predictor: how tall will my child be?
The mid-parental method averages both parents' heights, adds 6.5 cm for a boy or subtracts 6.5 cm for a girl, and halves the total. It gives one central estimate: genetics sets a range around it, around 8-10 cm wide, and factors like nutrition and the timing of puberty decide where inside that range a child actually lands.
It is a genetic centre point, not a forecast of any individual child. The published margin is about ±8.5 cm in either direction, which is wider than the 6.5 cm sex adjustment.
The mid-parental height formula
Boys: (father + mother + 13) ÷ 2 cm.
Girls: (father + mother − 13) ÷ 2 cm.
The result is a genetic midpoint, not a prediction — most children land within about ±8.5 cm of it.
| Father / mother (cm) | Predicted boy | Predicted girl |
|---|---|---|
| 180 / 165 | 179 cm | 166 cm |
| 175 / 160 | 174 cm | 161 cm |
| 170 / 155 | 169 cm | 156 cm |
This is the standard mid-parental formula; nutrition, sleep and general health also shape adult height. Related: BMI calculator and health guides.
Where the 6.5 cm comes from
The adjustment is half the average adult height difference between men and women in the reference population. Averaging the parents cancels their individual extremes; adding or subtracting that half-difference shifts the midpoint toward the child's likely sex-specific range. It is a deliberately crude method — a two-line formula standing in for a polygenic trait — and its published accuracy is ±8.5 cm at roughly the 90% level.
Worked example
Father 175 cm, mother 162 cm. Midpoint = (175 + 162) ÷ 2 = 168.5 cm.
Boy: 168.5 + 6.5 = 175 cm (175 ÷ 2.54 = 68.9 in).
Girl: 168.5 − 6.5 = 162 cm (63.8 in).
The page shows the midpoint and the adjustment separately so you can see which number moved: change the father to 185 cm and the midpoint rises to 173.5 cm, lifting the boy prediction to 180 cm.
What the number is good for
- A sanity check at a paediatric visit: a child tracking far below the mid-parental range is worth discussing, and that conversation is easier with a number.
- Clothing, bike and furniture sizing a few years ahead.
- Understanding why two siblings of the same parents can differ by 10 cm without anything being wrong.
What it cannot do
Height is polygenic: thousands of variants each contribute a fraction, and the parents' own heights capture only part of that. Nutrition, sleep, illness and puberty timing shift the outcome within the range; the formula cannot see any of them. It also says nothing about growth velocity, which is the measurement paediatricians actually track — a child can be short and growing normally, or average and falling away from their curve.
Mistakes to avoid
- Reading the single number as a prediction. The honest output is a range, roughly 166–184 cm for the boy in this example.
- Entering inches into a centimetre field. 5 ft 9 in entered as 59 gives a midpoint near 100 cm and a meaningless result.
- Using step-parent heights as if they were genetic. Only biological parents carry the information.
- Re-running the same numbers as a child grows. The prediction does not change with the child's current height, because the formula never used it.
Frequently Asked Questions
How accurate is the mid-parental method?
Published estimates put it within about ±8.5 cm for most children, which is a range of 17 cm end to end. It is a centre point for a conversation, not a forecast, and it cannot detect growth disorders.
Why add 6.5 cm for a boy and subtract for a girl?
It is half the average adult height difference between the sexes in the reference population. Averaging both parents gives a sex-neutral midpoint; the adjustment moves it into the child's likely range.
My child is already taller than the prediction at 12 — is the formula wrong?
Not necessarily. Children reach the midpoint at different ages, and early maturers can pass their adult prediction before 13. Track the growth curve rather than a single reading; paediatricians look at velocity over time.
Does the child's current height change the result?
No. This calculator uses only the two parents' heights and the child's sex, which is what the mid-parental method is defined as. A method that includes the child's current height and age is a different tool with different assumptions.
What if the parents are very different heights?
The average still applies, but the spread widens: children of a 195 cm and 150 cm pair have a midpoint of 172.5 cm and a genuinely wider likely range than children of two 172 cm parents.
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