The formula
How it works
Estimate how tall a child will grow as an adult from their parents’ heights, using the mid-parental method. Genetics set a strong baseline, and this simple formula gives a predicted adult height and a likely range.
FAQ
How accurate is this prediction?
It is a genetic estimate that most children land within about 8–10 cm (a few inches) of. Nutrition, health and other factors also matter, so treat the number as a likely middle of a range rather than a fixed outcome.
Why add or subtract 13 cm?
On average, adult men are about 13 cm (5 inches) taller than adult women. The formula adds that difference for boys and subtracts it for girls, then averages the parents’ heights to centre the estimate.
At what age is a child’s adult height easiest to predict?
Mid-parental prediction can be used from birth since it only needs the parents’ heights, but doctors get a more precise read once a child’s own growth curve is established, typically from around age 2 onward, and especially once puberty has started.
Does this work for adopted children or children of a single known parent?
It needs both biological parents’ heights, since it splits the genetic contribution evenly between them. If one biological parent’s height is unknown, the estimate cannot be calculated reliably from this method.
Can environmental factors change a child’s final height?
Yes. Genetics set the underlying potential, but chronic illness, poor nutrition or hormonal conditions during childhood can push actual adult height below the predicted range, while excellent nutrition and health tend to let a child reach the top of their genetic potential.
Why might siblings end up with different heights from the same prediction?
The mid-parental formula gives one estimate for a family, but each child inherits a different mix of the parents’ many height-related genes, so siblings normally land at different points within the same likely range rather than at the exact same height.
Is this the same method doctors use in clinic?
Yes, mid-parental height is a standard reference paediatricians use alongside a child’s own growth chart, though in clinical practice it is one data point among several rather than a standalone prediction.
About the height calculator
This calculator predicts a child’s adult height from the heights of their two parents, using the well-known mid-parental method. Height is strongly inherited, so a child’s eventual stature can be estimated surprisingly well just from their parents. The method blends the two parents’ heights and adjusts for the child’s sex, giving both a central prediction and the range most children fall within.
How to use it
Choose whether the child is a boy or a girl, pick centimetres or inches, and enter the mother’s and father’s heights. The calculator returns the predicted adult height and a likely range around it. For example, a boy whose mother is 165 cm and father is 180 cm has a predicted adult height of about 179 cm, give or take a few centimetres. Enter the parents’ heights as accurately as you can for the best estimate.
The formula
The mid-parental method averages the parents’ heights and shifts for sex. For a boy, ; for a girl, , where and are the mother’s and father’s heights in centimetres and 13 cm is the average difference between adult men and women. A range of about ±8.5 cm around this value covers most children.
Where it is used
Parents use it out of curiosity to picture how tall their children might become, and paediatricians use mid-parental height as a reference when checking whether a child’s growth is on track. It also comes up in sports, where predicted adult height can matter for young athletes. As a genetic estimate it is a guide, not a guarantee — real growth depends on health, nutrition and time.