Mid-parental height calculator
Mid-parental height is the average of the two parents’ heights, adjusted for the child’s sex: (father + mother) ÷ 2, plus 6.5 cm (2.5 in) for a boy or minus 6.5 cm for a girl. Doctors call the result the target height and usually quote a range of about ±8.5 cm (3.3 in) around it. Enter both parents’ heights to calculate it. This shows genetic potential only and is not medical advice.
Parents’ heights
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Target adult height
Enter both parents’ heights and press Calculate target height.
The mid-parental height formula
| Boys | (father’s height + mother’s height) ÷ 2, + 6.5 cm (about +2.5 in) |
| Girls | (father’s height + mother’s height) ÷ 2, − 6.5 cm (about −2.5 in) |
The 13 cm total reflects the average height difference between adult men and women. You will also see it written as (father + mother + 13 cm) / 2 for boys and (father + mother − 13 cm) / 2 for girls, which gives the same answer.
Worked example
Father 178 cm, mother 165 cm, child is a boy. Mid-parent = (178 + 165) / 2 = 171.5 cm. Add 6.5 cm: target 178 cm, with a range of about 169.5 to 186.5 cm.
Why there is a target range
Children scatter around their target height. The commonly used clinical range is about ±8.5 cm around the mid-parental value, so a target of 177 cm really means “probably somewhere between about 168 and 186 cm”. That is a wide window, which is why the formula is a starting reference and not a precise forecast.
Known limitations
The method tends to pull toward the average: for very tall parents it often comes out too low, and for very short parents too high. It ignores how the child is actually growing, and it assumes both heights are the biological parents’ and measured rather than guessed. If you know the child’s age, height and weight, the Khamis-Roche calculator uses that extra information. To see where a child stands today, use the height percentile calculator.
Common questions
- Is mid-parental height accurate?
- It is a fair estimate of genetic potential with a wide range (about ±8.5 cm). Methods that also use the child’s current measurements are usually tighter. See the method comparison.
- What units can I use?
- Centimetres, or feet and inches. You can also type a height like
5'10"or70indirectly. - What if I only know one parent’s height?
- The formula needs both. With one height missing there is no validated shortcut, so any result would be a guess.
Source: Tanner JM, Goldstein H, Whitehouse RH. “Standards for children’s height at ages 2–9 years allowing for height of parents.” Archives of Disease in Childhood. 1970;45:755–762. See About for all citations.