Family Height Calculator for Boys
Enter both parents' heights. Get a predicted adult height range for your son, using the standard mid-parental height formula pediatricians use.
Both parents' heights
Approximate is fine.
Estimated adult height
Midpoint of the estimated range
This is a statistical estimate using the mid-parental height formula with a ±8.5 cm (±3.3 in) confidence range. Real outcomes span an even wider window because puberty timing, nutrition, sleep, and genetic recombination all matter.
How the mid-parental height formula works
The mid-parental height formula is the most widely used clinical estimate for a child's adult height. It uses only two inputs: both biological parents' heights.
(Or, in inches: (Father's + Mother's + 5 in) ÷ 2)
The formula adjusts for the average height difference between adult men and women. The typical confidence range is ±8.5 cm (±3.3 in), meaning about two thirds of children fall within that window.
Why family height is the strongest single signal
Genetics accounts for about 80% of the variation in adult height. Parents' heights are the closest proxy for that genetic contribution , closer than any other single input. Studies of twins and family trees consistently confirm this.
That said, the mid-parental estimate is a range, not a guarantee. About one in three children ends up outside the ±8.5 cm window, and the range doesn't account for nutrition, illness, growth-timing differences, or genetic variation between siblings.
What this calculator doesn't tell you
It doesn't tell you where your son is right now on the growth curve. A boy tracking well below his mid-parental target at age 11 may catch up later, or may need a closer look. That trend , measured over time , is more diagnostic than any single prediction. The height percentile calculator shows you where he sits today; the Growth Check puts both together.
Frequently asked questions
How accurate is the mid-parental height formula?
The ±8.5 cm range captures roughly 68% of children (one standard deviation). About 95% of children fall within ±17 cm (±6.7 in). So it's a useful ballpark, not a prediction. Pediatricians use it as one data point among several , not on its own.
What if the parents are unusually tall or short?
The formula still works, but the confidence range widens. Genetic variation is greater at the extremes, and children of very tall or very short parents are more likely to end up closer to the population mean (a phenomenon called regression to the mean).
Does the mother's or father's height matter more for a boy?
Roughly equally. The formula weights both parents' heights the same and adds a fixed offset (13 cm for boys) to account for the average adult male-female height difference.
Should we use step-parent or adoptive parent heights?
No. Use biological parents' heights whenever possible. If one biological parent's height is unknown, the formula will be less reliable , a rough workaround is to use the population average (about 5'9" for U.S. men, 5'4" for U.S. women), but be aware the confidence range widens substantially.
My son is already outside the predicted range. What does that mean?
It could mean nothing , the formula misses one in three kids by definition. It could also mean he's still growing into or out of his family's range as puberty timing plays out. Sustained tracking well below (or well above) family expectation over years is more meaningful than a snapshot. If you're concerned, that's a conversation to have with his pediatrician.
The family height calculator is parent education, not medical advice or diagnosis. The mid-parental height formula is a widely used clinical estimate but has a wide confidence range and does not predict any individual child's actual adult height. If you have concerns about your son's growth, talk to his pediatrician. © 2026 The Growth Path.