Child Height Predictor

About This Tool

The mid-parent height formula is one of the most widely used methods for predicting a child's adult height. Developed from population studies, it provides a quick estimate based on the simple observation that tall parents tend to have tall children, and vice versa. While not perfectly accurate, it gives a reasonable prediction range that most children will fall within.

How the Mid-Parent Formula Works

The formula takes the average of both parents' heights, then adjusts for the sex of the child. Boys tend to be taller than girls, so 2.5 inches (6.35 cm) is added for boys and subtracted for girls. This adjustment accounts for the average height difference between adult men and women. The resulting prediction has a standard error of approximately 2 inches (5 cm), meaning roughly 68% of children will fall within 2 inches of the predicted height.

Factors Beyond Genetics

While genetics account for approximately 80% of height variation, the remaining 20% is influenced by nutrition (adequate protein, calcium, and vitamins during childhood), chronic illness, sleep quality (growth hormone is primarily released during deep sleep), and overall health. Children who experience malnutrition or chronic illness during critical growth periods may not reach their genetic potential. Conversely, improved nutrition in each generation is one reason children are often slightly taller than their parents.

When Children Reach Adult Height

Girls typically reach their adult height by age 14-16, about 2 years after the onset of puberty. Boys typically reach their adult height by age 16-18. Growth plates in the bones close at the end of puberty, which is when height gain stops. Pediatricians use growth charts and bone age X-rays to assess whether a child is on track to reach their predicted adult height.