Softonic

Adult Height Predictor Calculator

Step 1 / 4 Estimated adult height
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Enter the child’s sex and the biological mother’s and father’s heights to estimate a mid-parental target adult height. The calculator shows the target in centimeters and feet/inches, plus a typical target range of about ±10 cm because growth timing, health, and nutrition can still shift final height.

How to estimate an adult height

  1. 1

    Pick the child's sex

    Boys and girls use different constants because girls finish growing on average 2 years earlier than boys.

  2. 2

    Enter both parents' heights

    Use the biological parents' adult heights. Switch between centimeters and feet/inches if that is easier.

  3. 3

    Review the target range

    The result is a mid-parental target height plus a typical range of about ±10 cm on either side. It is a screening estimate, not a diagnosis.

  4. 4

    Use the range carefully

    Children can finish outside the range, especially with unusual puberty timing, chronic illness, or growth conditions. Ask a pediatrician about growth-curve concerns.

The mid-parental height formula

The classical pediatric formula (Tanner, 1970; still used by most pediatricians):

Boys:  ((father_cm + mother_cm) / 2) + 6.5
Girls: ((father_cm + mother_cm) / 2) - 6.5

Or equivalently in inches:

Boys:  ((father_in + mother_in) / 2) + 2.5
Girls: ((father_in + mother_in) / 2) - 2.5

The ±6.5 cm adjusts for the average sex difference in adult height. A boy whose parents are both 170 cm has a mid-parental target of 176.5 cm; his sister has a target of 163.5 cm.

Accuracy

Most published studies put the 95% confidence interval at roughly ±10 cm (±4 inches). That is a wide window — genetics accounts for about 80% of adult height variance, but nutrition, illness in childhood, hormonal conditions, and puberty timing supply the remaining 20%.

Method Typical 95% CI Input requirements
Mid-parental (Tanner) ±10 cm Parents’ heights
Khamis-Roche ±5–6 cm Age, height, weight, parent heights
Bone-age X-ray (Bayley-Pinneau) ±3–4 cm Bone-age radiograph

When to take the number seriously

  • Between ages 2 and puberty, the prediction tracks well for most children.
  • During puberty (girls 10-14, boys 12-16), growth is less predictable — a late bloomer and an early starter with the same current height can finish 10 cm apart.
  • After menarche (girls) or voice change (boys), the child has usually only 2 to 6 cm of growth left.

Red flags that warrant a pediatrician visit

  • Current height below the 3rd percentile or above the 97th for age.
  • Growth velocity drop of more than 2 cm/year compared to the previous year.
  • Puberty onset before age 8 (girls) or 9 (boys), or delay past 13 and 14 respectively.

Frequently Asked Questions

For the mid-parental formula, expect roughly ±10 cm at 95% confidence. Add-ons like the Khamis-Roche method (which includes weight) narrow it to about ±5 cm. Bone-age X-ray at puberty is the most accurate non-invasive option.

Both matter. Before puberty, the parents’ heights dominate because the child has years of growth ahead. After puberty the current height dominates because little growth remains.

Because adult men average about 13 cm taller than adult women. The mid-parental formula adds or subtracts 6.5 cm specifically to account for this average sex difference.

Not directly. If a parent height is unavailable, you can use the population average (about 175 cm for men, 162 cm for women in most Western countries) as a rough substitute, but the ±10 cm error margin widens further.

To a limited degree. Severe undernutrition or chronic illness in childhood can reduce adult height by 5 to 10 cm below the genetic potential. Once growth plates close (typically by 18-20 years) height is fixed.

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