How accurate is the mid-parental height formula?
The formula explains approximately 40–50% of variance in adult height — genetics is the strongest predictor but not the only one. For most children, the predicted value is within ±5 cm of actual adult height. The ±10 cm range covers the vast majority of outcomes, though outliers outside this range do occur.
Can I use current child height instead of parent heights?
Not with the mid-parental formula. This calculator is based on parental heights, not the child's current measurement. Other methods, such as bone-age prediction or growth-chart tracking, use the child's own measurements and can be more informative when a clinician is monitoring growth.
When should I ask a doctor about my child's height?
If a child is crossing centiles, growing much more slowly than expected, or seems very short or very tall compared with family pattern, a paediatrician should review the growth pattern. The calculator is best for broad estimation, not for ruling out growth problems.
Why does the result show a range instead of one exact adult height?
Because the mid-parental formula is a population estimate. Children with the same parent heights do not all finish at one number, so the ±10 cm band is often more useful than the midpoint alone when you are judging whether a growth pattern looks broadly in-family.
What is mid-parental height?
Mid-parental height is the average of both parents' heights, adjusted by a sex-specific offset to estimate a child's likely adult height. It is sometimes called target height, and it is a statistical estimate rather than a guarantee of the final result.
Can a bone-age scan predict adult height more accurately?
A bone-age assessment can add useful context when a clinician is reviewing a child's growth pattern, especially if puberty timing or a medical condition may be affecting height. It can improve interpretation, but it still does not turn the estimate into a certainty, and it is best used alongside a paediatric growth review.
Why does the same family show different target heights for a boy and a girl?
Because the formula starts with the same mid-parental midpoint and then applies a sex-specific offset. The boy row adds 6.5 cm and the girl row subtracts 6.5 cm, so the two target rows are 13 cm apart even though the parents' heights do not change.
How much does a small measuring error change the predicted height?
If both parents are measured 2 cm too high, the predicted target height also moves about 2 cm too high. If only one parent is off by 2 cm, the family midpoint changes by about 1 cm because the two heights are averaged first. That is why it is worth measuring adult heights carefully and without shoes before interpreting the result.
Does this calculator use the child's current age or current height?
No. This page is specifically a mid-parental height calculator, so it uses the parents' adult heights and the selected boy-or-girl formula only. It does not use current child age, current child height, weight, or bone age, which is one reason the result should be treated as a screening estimate instead of a personalised forecast.
What is the difference between predicted height and a height percentile?
Predicted height estimates the adult-height band that fits the family pattern. Height percentile shows where a child sits on a population growth chart at the current age. They are complementary tools: one gives family-based expectation and the other shows the current growth trajectory.
Can a child finish outside the usual ±10 cm band and still be healthy?
Yes. The band is useful because many children will finish somewhere inside it, but it is not a hard boundary between normal and abnormal. Puberty timing, nutrition, chronic illness, constitutional growth patterns, and wider genetic variation can all move final adult height above or below the usual band without automatically implying a disorder.
When is the mid-parental height formula less reliable?
It is less reliable when puberty timing is unusually early or late, when there are chronic medical or endocrine conditions, when the parental heights are measured poorly, or when the family pattern is unusual enough that a simple midpoint is not very representative. It is also weaker when the real question is clinical growth velocity rather than family expectation.
Should I use this result if my child already seems short for age?
You can use it as context, but not as reassurance by itself. If a child already seems short, is falling on formal growth charts, or is growing slowly, a paediatric review matters more than any single formula estimate. The best use of the calculator in that situation is to show the expected family band that the clinician can compare with the real growth pattern.
