How to use it
- Choose boy or girl.
- Enter the father's height.
- Enter the mother's height.
- Read the predicted adult height and the likely range.
The mid-parental height formula
Pediatricians use the mid-parental height (also called target height, from Tanner's method) to see whether a child's growth fits the family's genetic potential. Because adult men are on average about 13 cm (5 inches) taller than women, the formula adjusts one parent's height:
- Boys: (father's height + mother's height + 13 cm) ÷ 2, or + 5 in
- Girls: (father's height + mother's height − 13 cm) ÷ 2, or − 5 in
The likely range is the result ± 8.5 cm (about ± 3.3 inches). Most children end up somewhere within it.
Worked example
Father 5 ft 10 in (70 in), mother 5 ft 5 in (65 in).
- Son: (70 + 65 + 5) ÷ 2 = 70 in, or 5 ft 10 in. Likely range: about 5 ft 7 in to 6 ft 1 in.
- Daughter: (70 + 65 − 5) ÷ 2 = 65 in, or 5 ft 5 in. Likely range: about 5 ft 2 in to 5 ft 8 in.
The calculator does the conversion between feet, inches and centimeters for you and shows the exact decimal value too.
What else affects adult height
Genes explain most of the difference in height between people, but not all of it:
- Nutrition, especially in early childhood and puberty.
- Overall health: chronic illness, hormone problems and some medications can slow growth.
- Timing of puberty. Early bloomers grow sooner but may stop earlier; late bloomers often catch up.
- Sleep and physical activity support healthy growth.
Children don't always land in the middle of the range, and siblings can differ by several inches.
Other ways to predict height
- Growth chart tracking. Children usually follow a percentile curve. A child consistently on the 75th percentile tends to stay near it.
- Bone age. An X-ray of the hand and wrist shows how much growing time is left; doctors combine it with current height for a more precise prediction.
- Doubling height at age 2 is a popular rule of thumb (boys at 24 months, girls at 18 months), but it's rough.
Pediatricians typically use mid-parental height together with growth charts.
When to ask the pediatrician
Talk to your child's doctor if your child's height drops across two or more major percentile lines on the growth chart, is far below the mid-parental range, if growth seems to stop, or if puberty starts very early or very late. These can be signs of conditions that are treatable when caught early.
This calculator is informational only and isn't medical advice. Everything runs in your browser, and no data is saved.
Frequently asked questions
How accurate is the mid-parental height formula?
It gives a range that most children fall within (about ± 3.3 inches around the target), but it can't predict an individual child exactly.
How do I calculate my son's predicted height?
Add the father's and mother's heights in inches, add 5, and divide by 2. In centimeters, add 13 instead of 5.
How do I calculate my daughter's predicted height?
Add both parents' heights in inches, subtract 5, and divide by 2. In centimeters, subtract 13.
Can a child be taller than both parents?
Yes. The formula gives the average expectation; many children end up taller or shorter than predicted.
When do children stop growing?
Most girls reach adult height around 14–15 years and most boys around 16–18 years, but it varies.
Sources
- Tanner JM, Goldstein H, Whitehouse RH: Standards for children's height at ages 2–9 years allowing for heights of parents. Arch Dis Child 1970 (PubMed)
- WHO – Growth reference data for 5–19 years
- MedlinePlus Genetics – Is height determined by genetics?
Last reviewed: November 14, 2026 · Kitpebble editorial team
Change log
- : Sources expanded; FAQ and content reviewed.
For general information only; not medical advice or a diagnosis. How we write and review our pages