How to use the Child Height Predictor (Adult Height)
- Choose whether the child is a boy or a girl.
- Choose centimetres or inches.
- Enter the father’s and the mother’s heights.
- Read the predicted adult height and the likely range.
Formula used
Boys: (father’s height + mother’s height + 13 cm) ÷ 2. Girls: (father’s height + mother’s height − 13 cm) ÷ 2. The usual margin is about ±8.5 cm (3.3 inches).
Worked example
Here is the Child Height Predictor (Adult Height) worked through with the example values shown above, so you can check each step by hand.
| Inputs | |
|---|---|
| Child’s sex | Boy |
| Units | Centimetres |
| Father’s height | 175 |
| Mother’s height | 162 |
| Result | |
| Predicted adult height (cm) | 175 |
| In feet and inches | 5 ft 9 in |
| Likely range (about 95% of cases) | 167 to 184 cm (5 ft 6 in to 6 ft 0 in) |
The formula
For a boy: (father’s height + mother’s height + 13 cm) ÷ 2. For a girl: (father’s height + mother’s height − 13 cm) ÷ 2. The 13 cm is the average height gap between men and women. With a father of 175 cm and a mother of 162 cm, a boy is predicted to reach 175 cm (5 ft 9 in), and a girl 162 cm (5 ft 4 in).
The idea is that a child’s height tends to sit near the parents’ average, shifted for sex.
How wide the range is
The estimate is an average, and the spread around it is large. About 95% of children land within roughly 8.5 cm (3.3 inches) of it. For the default family that is 167 to 184 cm (5 ft 6 in to 6 ft 0 in).
Taller parents give taller predictions: a father of 185 cm and a mother of 170 cm give a boy 184 cm. In inches, a 70 inch father and a 64 inch mother give a boy 176.7 cm, which is 5 ft 10 in.
What else affects height
Genes from grandparents and other relatives, nutrition in childhood, long-term illness, sleep and the timing of puberty all play a part. A child who reaches puberty late may grow for longer and end up taller than a quick estimate suggests.
Heights also differ between populations and across generations, so a formula built on one group may be off for another.
When to talk to a doctor
A prediction is not a diagnosis. If a child is growing much more slowly than others the same age, or has crossed growth-chart lines downward, a paediatrician can check for causes and measure growth over time.
Growth charts, which compare a child’s height with others of the same age and sex, are a better tool for tracking progress than a single formula.
Frequently asked questions
How accurate is the prediction?
It is an average. About 95% of children end up within about 8.5 cm of it.
Does the child’s current height matter?
Not in this method. It uses only the parents’ heights.
Can I use inches?
Yes, choose inches and enter both parents’ heights in inches.
Why is a girl’s result lower?
On average, women are about 13 cm shorter than men, so the formula subtracts that amount.
What if a parent is unusually short or tall?
The estimate still works as a rough guide, but medical causes for unusual height can affect the child differently.
Can nutrition change the outcome?
Yes. Good nutrition and health during childhood help a child reach their genetic potential.
This calculator gives estimates for information only. Actual figures from a bank, employer, tax authority or doctor may differ. It is not financial, tax, legal or medical advice.