The mid-parental height method
A child’s adult height depends largely on genetics, so the parents’ heights give a useful first estimate. The mid-parental height (also called target height), introduced by James Tanner, is:
- Boy: (father’s height + mother’s height + 5 in) ÷ 2
- Girl: (father’s height + mother’s height − 5 in) ÷ 2
In centimeters, the adjustment is 13 cm, the average height difference between adult men and women. The calculator uses 6.5 cm (about 2.5 in) on either side of the parents’ average. About 95% of children reach an adult height within roughly 8.5 cm (3.3 in) of that target.
Worked example
The father is 70 inches (5 ft 10 in) tall and the mother 64.5 inches (5 ft 4.5 in). Their son’s target height:
- Parents’ average: (70 + 64.5) ÷ 2 = 67.25 in.
- Add 2.56 in for a boy: 69.8 in, about 5 ft 10 in or 177 cm.
- Usual range: 66.5 to 73.2 in, about 5 ft 6.5 in to 6 ft 1 in.
For a daughter of the same parents, the target would be about 64.7 inches (5 ft 4.7 in).
What else affects height
| Factor | Effect |
|---|---|
| Genetics | Explains most of the variation between people |
| Nutrition | Chronic undernutrition limits growth |
| Health | Celiac disease, hormone problems and chronic illness can slow growth |
| Puberty timing | Early developers often stop growing earlier |
| Sleep and activity | Support normal growth, but cannot raise genetic potential |
Other prediction methods
- Bone age: an X-ray of the left hand shows how much growth remains. Pediatric endocrinologists use it, especially around puberty.
- Khamis-Roche method: combines the parents’ heights with the child’s current height, weight and age, and is somewhat more accurate for children aged 4 to 17.
- Doubling height at age 2: an old rule of thumb that often lands close, but is less reliable than the methods above.
When to see a doctor
Track your child’s height on the CDC growth charts at checkups. Talk to your pediatrician if your child crosses two major percentile lines downward, grows less than about 2 inches (5 cm) a year between age 3 and puberty, or sits well below the range predicted from the parents’ heights. Most short children are healthy and simply follow their family pattern, but a medical check can rule out treatable causes.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.