Child Height Predictor

The most reliable everyday estimate of a child's adult height comes from the parents. The mid-parental height formula, used in paediatric clinics since the 1970s, averages both parents' heights and adjusts for the child's sex. Most children land within about 8.5 cm of it.

How it works

For a boy: add the mother's and father's heights in centimetres, add 13, and halve it. For a girl: add both heights, subtract 13, and halve it. The result is the mid-parental height; the usual range is that number plus or minus 8.5 cm (about 3⅓ inches), which covers roughly 19 in 20 children.

Questions parents ask

How accurate is the mid-parental height prediction?

It is a population estimate, not a promise. Roughly 95% of children end up within 8.5 cm of the mid-parental height. Nutrition, sleep, health and the timing of puberty all move the final number.

Is there a better predictor than parents' heights?

After about age 2, a child's own height percentile tends to track fairly steadily, so their current percentile on a growth chart is often a better guide than the formula. A bone-age X-ray gives the most precise estimate, and only a doctor orders that.

What if one parent is much taller than the other?

The formula still averages them. Children of parents with very different heights show more spread, so treat the range as more important than the single number.

Does this work for premature babies or children with growth conditions?

It assumes typical growth. If your child was born very early or has a condition that affects growth, their paediatrician's growth chart is the right reference.

Sources

• Tanner JM, Goldstein H, Whitehouse RH. Standards for children's height at ages 2-9 years allowing for height of parents. Arch Dis Child, 1970.
• NHS: Your baby's height and weight

Bheeli offers general guidance, not medical advice.